Blood & Lymphoreticular

Aplastic anemia: workup and treatment

Clinical Overview and When to Suspect Aplastic Anemia

— Idiopathic (~70%) — most common

— Drugs: chloramphenicol, carbamazepine, phenytoin, sulfonamides, gold, methimazole, NSAIDs, linezolid

— Toxins: benzene, pesticides, radiation

— Viral: seronegative hepatitis (2–5 mo post hepatitis, often in young men), EBV, parvovirus B19 (pure red cell), HIV

— Pregnancy (rare, often resolves postpartum)

— Inherited: Fanconi anemia, dyskeratosis congenita, Shwachman-Diamond

— Clonal overlap: PNH, hypoplastic MDS

— Young adult with fatigue + mucosal bleeding + recurrent infections and pancytopenia without splenomegaly or lymphadenopathy

— Patient on a culprit drug who develops cytopenias 2–8 weeks later

— Post-hepatitis pancytopenia in an adolescent male

— Pancytopenia with normal MCV or macrocytosis and low reticulocyte count

Definition: Aplastic anemia (AA) is a syndrome of bone marrow failure characterized by pancytopenia with a hypocellular marrow (<25% cellularity, or 25–50% with <30% residual hematopoietic cells), without abnormal infiltrate or fibrosis.

Pathophysiology: Immune-mediated destruction of CD34+ hematopoietic stem cells by autoreactive cytotoxic T cells producing IFN-γ and TNF-α in most acquired cases; inherited forms reflect intrinsic stem cell defects (telomere maintenance, DNA repair).

Epidemiology: Bimodal — peaks at ages 15–25 and >60. Incidence ~2 per million in the West; 2–3x higher in East Asia. M=F.

Etiologies to anchor in a stem:

When to suspect on Step 3:

Board pearl: The triad pointing to AA over leukemia/lymphoma is pancytopenia + low retic + NO organomegaly, NO blasts, NO lymphadenopathy. Splenomegaly should redirect you toward MDS, hairy cell leukemia, or hypersplenism.

Step 3 management anchor: Suspicion → CBC with diff, retic count, peripheral smear → urgent bone marrow biopsy with cytogenetics → simultaneously screen for PNH, hepatitis, HIV, B12/folate, and consider germline testing if <40 or syndromic features.

Presentation Patterns and Key History

— Anemia: progressive fatigue, exertional dyspnea, pallor, headache, palpitations — usually subacute over weeks, not abrupt

— Thrombocytopenia: mucocutaneous bleeding — petechiae on lower extremities, gingival bleeding when brushing teeth, epistaxis, menorrhagia, easy bruising

— Neutropenia: recurrent or unusually severe bacterial infections, oral ulcers, perirectal pain/abscess, fever without localizing source

— Drug exposures (last 6 months): chloramphenicol, sulfa antibiotics, anticonvulsants (carbamazepine, phenytoin), methimazole/PTU, gold, NSAIDs, linezolid, chemotherapy

— Occupational/environmental: benzene (rubber, petroleum, dry cleaning), pesticides, radiation exposure, glue sniffing

— Recent illnesses: hepatitis symptoms 2–6 months prior (jaundice, RUQ pain), viral prodromes, parvovirus contacts, HIV risk factors

— Family history: early gray hair, pulmonary fibrosis, liver cirrhosis (dyskeratosis congenita); short stature, café-au-lait spots, thumb anomalies (Fanconi)

— Pregnancy status in any woman of childbearing age

— Bleeding history quantified: pad counts, episodes requiring ED visits

— Bone pain → leukemia, metastatic disease

— B symptoms (drenching sweats, weight loss) → lymphoma, MDS

— Joint pain, photosensitivity → SLE-associated cytopenia

— Dark urine, abdominal pain, thrombosis → consider PNH overlap

Symptom triad maps to the cytopenia:

Tempo clue: Symptoms typically evolve over weeks to a few months. Hyperacute pancytopenia (days) suggests acute leukemia or drug-induced agranulocytosis instead.

Targeted history must capture:

Red flags that change the differential:

Key distinction: AA causes pancytopenia without constitutional B symptoms. Significant weight loss, drenching night sweats, or bone pain should push you away from AA toward malignancy.

Board pearl: A male teenager presenting with pancytopenia 2–3 months after an episode of acute hepatitis (often seronegative for A/B/C/E) is the classic vignette for post-hepatitis aplastic anemia — prognosis is poor without urgent transplant referral.

Physical Exam Findings (and Hemodynamic Assessment)

— Tachycardia and orthostatic hypotension if Hb critically low or active bleeding

— Fever — assume neutropenic fever if ANC <500 and treat as emergency

— SpO₂ — hypoxia suggests pulmonary hemorrhage or pneumonia

— Petechiae on dependent areas (ankles, hard palate), wet purpura on buccal mucosa (predicts CNS bleed risk)

— Ecchymoses without trauma history

— Conjunctival pallor, scleral icterus absent (presence suggests hemolysis → reconsider PNH, autoimmune hemolysis)

— Oral ulcers, gingivitis, perirectal tenderness

— No hepatosplenomegaly

— No lymphadenopathy

— No bone tenderness (sternal tenderness suggests leukemia)

— Fanconi anemia: short stature, café-au-lait macules, hypoplastic/absent thumbs, microcephaly, hypogonadism, renal anomalies

— Dyskeratosis congenita: mucocutaneous triad — oral leukoplakia, dystrophic nails, reticular skin pigmentation; premature graying, pulmonary fibrosis

— Shwachman-Diamond: steatorrhea, short stature, metaphyseal dysostosis

— Active mucosal bleeding + platelets <10K → high risk for ICH; assess neuro status, transfuse platelets, hold antiplatelets/anticoagulants

— Hemodynamic instability from anemia → type and crossmatch, transfuse PRBCs targeting Hb ≥7 (≥8 if cardiac disease)

General appearance: Pale, fatigued-appearing patient; may be febrile if neutropenic.

Vital signs to obtain in CCS:

Skin and mucosa:

Crucially absent findings (their absence supports AA):

Findings suggesting inherited marrow failure (do not miss in young patients):

Hemodynamic assessment priority:

CCS pearl: On a CCS case, the moment you see petechiae + fever + pallor in a young patient, order CBC with diff, retic, peripheral smear, blood cultures ×2, and place the patient in a protective isolation room before the marrow result returns.

Board pearl: Splenomegaly essentially excludes acquired AA — redirect to hypersplenism, MDS, hairy cell leukemia, or visceral leishmaniasis.

Diagnostic Workup — Initial Labs / Imaging / Biomarkers

— Pancytopenia with low Hb, low ANC, low platelets

— MCV often normal or mildly macrocytic (stress erythropoiesis, fetal Hb)

— No blasts, no immature granulocytes

— Absolute reticulocyte count <60,000/µL is characteristic

— Retic index <1% confirms hypoproliferative marrow

— Normochromic, normocytic or macrocytic RBCs

— No teardrop cells (excludes myelofibrosis), no blasts (excludes leukemia), no dysplastic forms (raises MDS), no schistocytes (excludes TMA)

— Decreased platelets without giant forms

— Severe AA (SAA): marrow cellularity <25%, plus 2 of 3: ANC <500, platelets <20,000, absolute retic <60,000

— Very severe AA (VSAA): SAA criteria + ANC <200

— Non-severe AA: doesn't meet SAA criteria

— Reticulocyte count, LDH, haptoglobin, indirect bilirubin (assess hemolysis/PNH)

— B12, folate, copper, zinc (reversible mimics)

— Hepatitis A/B/C, HIV, EBV, CMV, parvovirus B19

— ANA, anti-dsDNA (SLE)

— TSH, iron studies, ferritin

— Pregnancy test in women of childbearing age

— HLA typing of patient and siblings — order at diagnosis to expedite transplant planning

— CXR for infection

— CT abdomen if hepatosplenomegaly or lymphadenopathy on exam to exclude lymphoproliferative disease

CBC with manual differential — the cornerstone:

Reticulocyte count and index:

Peripheral blood smear — look carefully:

Severity grading (Camitta criteria) — memorize:

Mandatory adjunct labs:

Imaging:

Board pearl: A normal or elevated EPO level with a low retic count in a pancytopenic patient is classic for marrow failure — the marrow can't respond to the EPO signal.

Step 3 management: Order HLA typing on patient and all full siblings simultaneously with the bone marrow biopsy — do not wait for biopsy results. Time to transplant is the single biggest modifiable prognostic factor in severe AA.

Diagnostic Workup — Advanced or Confirmatory Studies

— Biopsy ≥1 cm core preferred; aspirate alone underestimates cellularity

— Hypocellular marrow with fatty replacement: <25% cellularity, or 25–50% with <30% residual hematopoiesis

— Remaining cells appear morphologically normal; no fibrosis, no infiltrate, no dysplasia, <5% blasts

— If dysplasia or blasts present → reclassify as MDS or AML

— Normal karyotype expected in AA

— Clonal abnormalities (–7, +8, del(5q), del(20q)) suggest hypoplastic MDS rather than AA

— Monosomy 7 carries poor prognosis and pushes toward early transplant

— Test peripheral blood granulocytes and RBCs for CD55 and CD59 deficiency using FLAER (fluorescent aerolysin)

— Small PNH clones found in ~50% of AA patients — supports immune pathogenesis and predicts good response to immunosuppression

— Large clones (>50%) with hemolysis → classic PNH, treat with eculizumab/ravulizumab

— Order in all patients <40 and in any patient with syndromic features

— Detects Fanconi anemia — critical because these patients cannot tolerate standard conditioning chemotherapy or ATG

— Very short telomeres (<1st percentile) → dyskeratosis congenita / telomere biology disorders

— Affects donor choice and conditioning intensity

Bone marrow aspirate AND biopsy — required for diagnosis:

Cytogenetics on marrow:

Flow cytometry for PNH clone:

Chromosomal breakage testing (mitomycin C or DEB):

Telomere length testing (lymphocyte flow-FISH):

Germline genetic panel: Sequencing for TERT, TERC, DKC1, RTEL1, TINF2, FANC genes if young, family history, or syndromic.

Vitamin assays: Copper deficiency mimics AA and is reversible — always check copper in patients with bariatric surgery, zinc supplementation, or TPN.

Key distinction: Hypoplastic MDS vs AA — both have hypocellular marrows. Cytogenetic abnormalities, dysplasia in residual cells, and increased blasts point to MDS. This distinction changes management dramatically.

Board pearl: Always rule out Fanconi anemia in patients <40 before giving ATG or transplant conditioning — missed diagnosis leads to lethal regimen-related toxicity.

Risk Stratification and First-Line Management Logic

— Requires definitive therapy — supportive care alone has ~80% 1-year mortality

— Two definitive options: matched sibling donor (MSD) hematopoietic stem cell transplant (HSCT) or immunosuppressive therapy (IST) with horse ATG + cyclosporine + eltrombopag

— Transfusion-independent patients with mild cytopenias → observe with close monitoring

— Transfusion-dependent or symptomatic → treat as severe

— Age <50 + matched sibling donor available → HSCT first-line (long-term survival ~80–90%)

— Age <50, no MSD → IST first-line, then matched unrelated donor (MUD) transplant if no response at 6 months

— Age 50–75, fit → IST first-line; MUD transplant for relapse or refractoriness in selected fit patients up to ~70

— Age >75 or unfit → IST + supportive care; transplant generally not pursued

— Transfusion support (irradiated, leukoreduced, CMV-safe products)

— Infection prophylaxis if ANC <500: antibacterial (fluoroquinolone), antifungal (posaconazole), antiviral (acyclovir)

— G-CSF not routinely recommended as primary therapy

— Iron chelation if >20 transfusions or ferritin >1000

— Family member blood product donations (alloimmunization risk)

— Unnecessary transfusions

— Live vaccines

Severity drives urgency and modality — apply Camitta criteria immediately after marrow biopsy.

Severe (SAA) or Very Severe AA (VSAA):

Non-severe AA:

First-line decision algorithm (memorize):

Why age 50 matters: Transplant-related mortality rises sharply with age and comorbidity; IST response rates remain ~60–70% across ages but durable remissions favor younger.

Supportive care started immediately in parallel:

Avoid in potential transplant candidates:

Step 3 management: Within 24–48 hours of diagnosis: HLA-type patient and siblings, refer to a transplant center, initiate transfusion support with irradiated/leukoreduced products, and start neutropenic precautions. Do not delay referral while completing germline workup.

Board pearl: The single best predictor of long-term survival in young SAA patients is time from diagnosis to definitive therapy — every week of delay increases infection mortality.

Pharmacotherapy — First-Line Drug Regimen (Immunosuppressive Therapy)

— Horse antithymocyte globulin (h-ATG) 40 mg/kg/day IV ×4 days

— Cyclosporine (CSA) 5 mg/kg/day PO divided BID, target trough 200–400 ng/mL, continued ≥6 months then slow taper over 12+ months

— Eltrombopag 150 mg PO daily (50 mg in East Asian patients), started day 1, continued ≥6 months

— Methylprednisolone 1 mg/kg/day during ATG infusion to prevent serum sickness, tapered over 2 weeks

— Acetaminophen, diphenhydramine, methylprednisolone

— Test dose to assess hypersensitivity

— Platelet transfusion to keep platelets >30,000 during infusion (ATG causes severe thrombocytopenia)

— ATG: fever, chills, rash, serum sickness (5–14 days post-infusion — arthralgia, fever, rash; treat with steroids)

— Cyclosporine: nephrotoxicity, hypertension, hyperkalemia, hypomagnesemia, gingival hyperplasia, hirsutism, tremor

— Eltrombopag: hepatotoxicity (monitor LFTs), thromboembolism, cataracts with chronic use

— Evaluate at 3 and 6 months

— Response = transfusion independence + ANC >500 + platelets >20,000

— ~60–70% respond; ~30% achieve complete response with triple therapy

— Relapse occurs in ~30% — may respond to CSA reintroduction or second course of ATG (rabbit)

— Clonal evolution to MDS/AML/PNH in ~10–15% over 10 years

Standard IST triple regimen — current first-line for non-transplant candidates:

Why horse ATG, not rabbit: Multiple RCTs (NIH) show horse ATG superior response (~68% vs ~37%) and survival vs rabbit ATG in first-line SAA. Use rabbit ATG only for relapse.

Eltrombopag mechanism and impact: TPO-receptor agonist stimulates residual stem cells; addition to ATG+CSA raised complete response rates from ~10% to ~40% and overall response to ~80%.

Premedications for ATG:

Common adverse effects to anticipate:

Response assessment:

Board pearl: Cyclosporine taper must be slow — abrupt discontinuation causes relapse in up to 50%. Taper over 12+ months after response.

Step 3 management: Monitor cyclosporine trough weekly initially, BMP weekly, magnesium replacement aggressive, BP at every visit. Adjust dose for creatinine rise >30%.

Procedures — Hematopoietic Stem Cell Transplantation

— SAA/VSAA patients age <50 (some centers <40) with a matched sibling donor (MSD)

— Increasingly considered first-line with matched unrelated donors (MUD) in younger patients at experienced centers

— Failure to respond to IST at 6 months

— Relapse after IST

— Clonal evolution to MDS

— Standard: cyclophosphamide 200 mg/kg + ATG for MSD

— For MUD or older patients: fludarabine + cyclophosphamide + ATG ± low-dose TBI 2 Gy

— Avoid high-dose busulfan/TBI — increases late malignancy

— Fanconi anemia: use fludarabine + low-dose cyclophosphamide ± ATG, NO standard-dose alkylators or full TBI (lethal toxicity)

— Bone marrow preferred over peripheral blood in AA — lower rates of chronic GVHD

— Cord blood reserved for pediatric patients without other donors

— MSD HSCT in young patients: 5-year OS 80–90%

— MUD HSCT: 5-year OS 70–80%

— Haploidentical HSCT: improving, 60–70% in experienced centers

— Graft failure (5–10%) — primary or secondary

— Acute GVHD (skin rash, diarrhea, hepatitis) — 20–40%

— Chronic GVHD — 20–30%, lower with bone marrow source

— Infections: CMV reactivation, invasive fungal, PCP — prophylaxis required

— Late malignancies: secondary MDS/AML, solid tumors (especially oral SCC, skin) — lifelong surveillance

— Avoid family donor blood products (alloimmunization)

— Iron chelation if ferritin >1000

— Fertility preservation counseling

— Dental clearance, infectious screening

Indication for HSCT as first-line:

Indication for HSCT as second-line:

Conditioning regimen — reduced intensity in AA (no leukemia to eradicate):

Stem cell source:

GVHD prophylaxis: Cyclosporine + methotrexate, or post-transplant cyclophosphamide in haploidentical settings.

Outcomes:

Major complications:

Pre-transplant must-dos:

CCS pearl: When transplant is on the table, order HLA typing on all full siblings simultaneously, refer to transplant center, and avoid all unnecessary transfusions. Use CMV-seronegative or leukoreduced, irradiated products universally.

Board pearl: In AA, bone marrow stem cell source beats peripheral blood for chronic GVHD reduction — opposite of many malignant indications.

Special Populations — Elderly and Renal/Hepatic Impairment

— Transplant-related mortality rises sharply >50; most centers cap MSD HSCT at ~65–70 in highly fit patients only

— IST remains first-line for most patients >50; response rates similar (~60–70%) but durability and tolerance lower

— Eltrombopag well-tolerated in elderly; dose unchanged

— Higher baseline infection risk → lower threshold for prophylactic antibiotics/antifungals when ANC <500

— Higher risk of clonal evolution to MDS/AML post-IST — monitor with serial CBCs and marrow exams

— Cardiac (ECG, echo) — anthracycline-naive but cyclosporine causes hypertension

— Pulmonary function (DLCO) before transplant

— Renal function — cyclosporine dose adjustment

— HCT-CI (Hematopoietic Cell Transplant Comorbidity Index) guides transplant eligibility

— Cyclosporine is nephrotoxic — start at lower end (3 mg/kg/day) if baseline CKD; monitor creatinine q3–7 days initially

— Hold or reduce dose if creatinine rises >30% from baseline

— Alternative: tacrolimus has similar efficacy and sometimes used if CSA intolerance

— Avoid concurrent NSAIDs, aminoglycosides, IV contrast

— Adjust acyclovir, fluconazole prophylaxis for CrCl

— Eltrombopag is hepatotoxic — baseline LFTs, then weekly ×4, then monthly

— Hold for ALT >3× ULN with bilirubin rise or symptomatic hepatitis

— Reduce starting dose to 25 mg daily in moderate–severe hepatic impairment (Child-Pugh B/C)

— In post-hepatitis AA, ATG and CSA may be cautiously used but liver function dictates

— Cyclosporine: CYP3A4 substrate — avoid azoles, macrolides, grapefruit; statins limited to low-dose pravastatin/rosuvastatin (rhabdomyolysis risk)

— Eltrombopag chelates polyvalent cations — separate from calcium, antacids, iron by 4 hours

Elderly (≥60) considerations:

Comorbidity screening before therapy:

Renal impairment management:

Hepatic impairment:

Drug interactions to anticipate:

Board pearl: A patient on cyclosporine who develops a 40% rise in creatinine, hyperkalemia, and hypomagnesemia has calcineurin inhibitor nephrotoxicity — dose-reduce, don't discontinue (relapse risk).

Step 3 management: In elderly patients on IST, schedule CBC weekly ×8 weeks, then biweekly, then monthly; LFTs, BMP, CSA trough at each visit; marrow biopsy at 6 months to assess response and clonal evolution.

Special Populations — Pregnancy, Pediatrics, and Inherited Syndromes

— Rare; can occur in any trimester, sometimes recurs with subsequent pregnancies

— May remit spontaneously postpartum

— Cyclosporine is the preferred agent during pregnancy (category C but extensive safety data)

— ATG generally avoided in pregnancy due to limited data; eltrombopag avoided

— Aggressive transfusion support (irradiated, leukoreduced, CMV-safe) to maintain Hb >8, platelets >20K (>50K before delivery, >80K for neuraxial anesthesia)

— Multidisciplinary care: hematology, MFM, anesthesia

— Mode of delivery dictated by obstetric indications; vaginal preferred if platelets adequate

— Higher proportion of inherited marrow failure syndromes — always test for Fanconi anemia (chromosomal breakage) and dyskeratosis congenita (telomere length) before treatment

— HSCT from matched sibling is first-line for pediatric SAA — 5-year OS >90%

— IST reserved for those without an MSD; eltrombopag approved down to age 2

— Growth, fertility, late effects all major considerations

— Autosomal recessive (mostly), DNA crosslink repair defect

— Median age of marrow failure ~7 years

— Cannot tolerate standard conditioning — must use fludarabine-based reduced-intensity regimen with low-dose cyclophosphamide

— Lifetime cancer risk: AML, head/neck SCC, vulvar SCC — surveillance starts in adolescence

— Screen siblings before using as donor

— Mucocutaneous triad + marrow failure + pulmonary fibrosis + liver disease

— Avoid alkylators and TBI in conditioning; use fludarabine-based reduced intensity

— IST less effective than in acquired AA

— Androgens (danazol) can improve cytopenias by upregulating telomerase

Pregnancy-associated AA:

Pediatric AA — key differences:

Fanconi anemia (FA):

Dyskeratosis congenita / telomere biology disorders:

Shwachman-Diamond: Pancreatic insufficiency + neutropenia + skeletal anomalies; risk of MDS/AML.

Key distinction: A young patient with pancytopenia, short stature, abnormal thumbs, café-au-lait spots has Fanconi anemia until proven otherwise — order DEB/MMC chromosomal breakage testing before any cytotoxic therapy.

Board pearl: Danazol (androgen) is uniquely useful in telomere disorders — upregulates telomerase, improves blood counts; not used in acquired AA first-line.

Complications and Adverse Outcomes

— Neutropenic fever (ANC <500 + temp ≥38.3 once or ≥38.0 sustained) — medical emergency

— Bacterial: gram-negatives (E. coli, Pseudomonas, Klebsiella), gram-positives (coag-neg staph, viridans strep)

— Invasive fungal: Aspergillus, Candida, mucormycosis — risk rises after 7–10 days of profound neutropenia

— Viral reactivation: HSV, VZV, CMV (especially post-transplant)

— Treat empirically with cefepime or piperacillin-tazobactam, add vancomycin if line infection/MRSA risk, add antifungal if fever >4–7 days

— Mucocutaneous bleeding common at platelets <20K

— Intracranial hemorrhage — leading cause of bleeding death; risk highest with platelets <10K plus headache/hypertension

— Transfuse platelets prophylactically <10K, <20K if febrile, <50K for procedures

— Iron overload after ~20 RBC transfusions — cardiomyopathy, hepatic fibrosis, endocrinopathies

— Alloimmunization — refractoriness to platelet transfusions, harder transplant

— Transfusion-associated GVHD — prevent with irradiation of all cellular products

— TRALI, TACO, hemolytic reactions

— ATG serum sickness — fever, rash, arthralgia 7–14 days post-infusion; treat with steroids

— Cyclosporine: nephrotoxicity, HTN, neurotoxicity (PRES), gingival hyperplasia, hirsutism

— Eltrombopag: hepatotoxicity, thromboembolism, cataracts

— Transplant: GVHD (acute and chronic), graft failure, veno-occlusive disease, late malignancies

— ~10–15% of IST-treated patients develop MDS, AML, or clinical PNH over 10 years

— Risk factors: older age, longer time to response, monosomy 7

— Monitor with periodic marrow biopsies and cytogenetics

Infectious complications — leading cause of early mortality:

Bleeding complications:

Transfusion-related complications:

Treatment-related complications:

Clonal evolution — major long-term concern:

Reproductive complications: Infertility after transplant conditioning; offer fertility preservation pre-treatment.

Board pearl: All cellular blood products in AA patients must be irradiated and leukoreduced for life — prevents transfusion-associated GVHD and CMV transmission, and reduces alloimmunization.

Step 3 management: Neutropenic fever protocol — within 1 hour: blood cultures ×2 (peripheral + line), urine culture, CXR, broad-spectrum antibiotic (cefepime), admit to hospital. Do not wait for ANC confirmation if clinical suspicion is high.

When to Escalate Care — ICU, Consult, Inpatient Triage

— Newly diagnosed SAA/VSAA — admit for workup, transfusions, infection prophylaxis initiation

— Neutropenic fever (ANC <500 + temp ≥38.3°C)

— Active bleeding with platelets <20K

— Hemodynamic instability from anemia

— Initiation of ATG (4-day inpatient infusion at most centers)

— Septic shock or hemodynamic instability despite resuscitation

— Respiratory failure (pulmonary hemorrhage, ARDS from sepsis, transfusion reactions)

— Intracranial hemorrhage with neurologic deterioration

— Severe ATG reaction — anaphylaxis, cardiopulmonary compromise

— Tumor lysis-like syndrome (rare in AA, more in lymphoid malignancy mimics)

— Hematology/oncology — primary management

— Transplant center referral — within days of diagnosis if age <50 or transplant candidate; do not wait for IST failure

— Infectious disease — for resistant infections, fungal disease

— Genetics — for suspected inherited marrow failure

— Gynecology/reproductive endocrinology — fertility preservation before therapy

— Dental — pre-transplant clearance

— ATG infusion typically requires inpatient admission (4 days) for monitoring of anaphylaxis, cytokine release, severe thrombocytopenia

— CSA + eltrombopag continued outpatient with close lab monitoring

— Platelets: prophylactic transfusion <10K, <20K if febrile/infection, <50K for procedures, <100K for neurosurgery or ophthalmologic surgery

— RBCs: target Hb ≥7 (≥8 if cardiac disease, active bleeding)

— All products: irradiated, leukoreduced, CMV-safe (seronegative or filtered)

Immediate hematology consult at diagnosis — AA is a tertiary-care disease; community management is inappropriate beyond initial stabilization.

Inpatient admission criteria:

ICU transfer triggers:

Specialist consultations to obtain early:

Outpatient vs inpatient IST:

Transfusion thresholds:

CCS pearl: On a CCS case, the moment SAA is confirmed: admit to hematology service in a protective isolation room, consult hematology, send HLA typing on siblings, initiate fluoroquinolone + posaconazole + acyclovir prophylaxis if ANC <500, and refer to a transplant center on day 1.

Board pearl: Do not delay transplant referral while completing IST — referral at diagnosis allows parallel donor search and faster definitive therapy if IST fails or relapses.

Key Differentials — Same-Category (Marrow Failure / Cytopenia)

— Hypocellular marrow overlapping AA, but cytogenetic abnormalities (–7, +8, del(5q), del(20q)) and dysplasia in residual cells

— More common in older adults; risk of AML transformation higher

— Treatment differs: hypomethylating agents (azacitidine), transplant; IST can also work in hypocellular MDS

— GPI-anchor deficiency from somatic PIGA mutation

— Triad: hemolytic anemia + cytopenias + thrombosis (hepatic veins → Budd-Chiari, mesenteric, cerebral sinus)

— Smooth muscle dystonias (abdominal pain, dysphagia, ED)

— FLAER flow cytometry on granulocytes confirms

— Treat with eculizumab or ravulizumab (terminal complement inhibitors); meningococcal vaccine required

— Overlap with AA in ~50% — small PNH clones common in AA

— Pancytopenia possible without circulating blasts

— Marrow biopsy distinguishes — ≥20% blasts = AML

— Often with bone pain, organomegaly, lymphadenopathy

— Teardrop cells and leukoerythroblastic smear

— Splenomegaly prominent

— Marrow biopsy: fibrosis on reticulin stain — opposite of AA

— Clonal cytotoxic T cells

— Neutropenia predominates; often associated with RA

— Flow + TCR clonality on blood/marrow

— Pancytopenia + splenomegaly + monocytopenia

— Hairy cells on smear; BRAF V600E mutation

— Treat with cladribine

— Pure red cell aplasia with reticulocytopenia and giant pronormoblasts in marrow

— Typically in sickle cell, hereditary spherocytosis, or immunocompromised patients

— Self-limited or treated with IVIG

Hypoplastic MDS:

Paroxysmal nocturnal hemoglobinuria (PNH):

Acute leukemia (especially aleukemic AML):

Myelofibrosis:

Large granular lymphocyte (LGL) leukemia:

Hairy cell leukemia:

Aplastic crisis from parvovirus B19:

Key distinction: AA shows hypocellular marrow without dysplasia, blasts, fibrosis, or infiltrate and is multilineage. Pure red cell aplasia affects only erythroid line; agranulocytosis affects only neutrophils.

Board pearl: Splenomegaly + pancytopenia is essentially NEVER aplastic anemia — think MDS, myelofibrosis, hairy cell, hypersplenism (cirrhosis), or visceral leishmaniasis.

Key Differentials — Other-Category Causes of Pancytopenia

— B12 deficiency: macrocytic anemia, hypersegmented neutrophils, mild pancytopenia possible; neurologic signs

— Folate deficiency: similar smear, no neurologic findings

— Copper deficiency: sideroblastic anemia with neutropenia, often macrocytic; seen in bariatric surgery, zinc supplementation, TPN

— Replace and recheck before labeling as AA

— HIV — direct marrow effect plus opportunistic infections

— Disseminated tuberculosis or histoplasmosis — marrow granulomas

— Visceral leishmaniasis (kala-azar) — splenomegaly, fever, pancytopenia

— Severe sepsis — transient pancytopenia

— Brucellosis, ehrlichiosis

— SLE — autoimmune cytopenias, often AIHA + ITP + leukopenia; ANA/dsDNA positive

— Felty syndrome (RA + splenomegaly + neutropenia)

— Chemotherapy (predictable, dose-dependent)

— Methotrexate, azathioprine, mycophenolate

— Linezolid (especially >2 weeks)

— Valganciclovir, ganciclovir

— Trimethoprim-sulfamethoxazole

— Cirrhosis, portal hypertension, Gaucher disease

— Pooling/sequestration causes pancytopenia

— Marrow is normocellular or hypercellular, opposite of AA

— Solid tumor metastasis to marrow (breast, prostate, lung, GI)

— Leukoerythroblastic smear with teardrop cells; marrow shows tumor

— Fever, splenomegaly, cytopenias ≥2 lines, ferritin >500 (often >10,000), elevated triglycerides, low fibrinogen, hemophagocytosis in marrow

— Critical to recognize — high mortality, requires HLH-94 protocol

— Gelatinous marrow transformation, mild pancytopenia, reversible with refeeding

Nutritional deficiencies (reversible — must screen):

Infections causing pancytopenia:

Autoimmune diseases:

Medications causing marrow suppression (distinct from idiosyncratic AA):

Hypersplenism:

Metastatic infiltration:

Hemophagocytic lymphohistiocytosis (HLH):

Anorexia nervosa:

Key distinction: Marrow cellularity is the great divider — AA = hypocellular; infiltrative/leukemic/hemolytic causes = normo/hypercellular; nutritional = often hypercellular with megaloblastic changes.

Board pearl: Always check B12, folate, and copper before labeling pancytopenia as aplastic anemia — these are fully reversible and missed diagnoses are exam favorites.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Cyclosporine 5 mg/kg/day divided BID, with prescribed home INR-style monitoring (trough levels)

— Eltrombopag 150 mg PO daily (50 mg East Asian), separated from polyvalent cations by 4 hours

— Prednisone taper following ATG to prevent serum sickness

— Infection prophylaxis while ANC <500–1000:

— Antibacterial: levofloxacin 500 mg daily

— Antifungal: posaconazole 300 mg daily (after loading)

— Antiviral: acyclovir 400 mg BID

— TMP-SMX for PCP prophylaxis post-transplant

— Magnesium oxide supplement for CSA-induced hypomagnesemia

— Antihypertensives if needed (avoid ACE-I early due to hyperkalemia with CSA; amlodipine preferred)

— Calcineurin inhibitor (CSA or tacrolimus) + methotrexate prophylaxis tapered over months

— TMP-SMX for PCP × 6–12 months

— Acyclovir/valacyclovir × 1 year

— Antifungal prophylaxis during immunosuppression

— CMV monitoring with PCR weekly

— Avoid benzene, pesticides, organic solvents

— No live vaccines while immunosuppressed

— Sun protection (skin cancer risk, especially post-transplant)

— Avoid raw/undercooked foods, sick contacts

— Smoking cessation, alcohol moderation

— Post-transplant: full revaccination starting 6–12 months (inactivated only initially; live vaccines deferred ≥2 years and only if off immunosuppression with normal counts)

— Annual influenza (inactivated), COVID-19, pneumococcal series

— Meningococcal vaccine if eculizumab/PNH overlap

— Annual skin exam (post-transplant SCC, BCC risk)

— Oral exam every 6 months for SCC (especially Fanconi/DC)

— Gynecologic exam annually (HPV-driven cancers higher in transplant patients)

Discharge medications after IST initiation:

Post-transplant medications:

Lifestyle and exposure counseling:

Vaccinations:

Cancer surveillance:

Board pearl: Patients on eltrombopag must separate the dose by at least 4 hours from antacids, dairy, calcium, iron, and multivitamins — chelation drops absorption dramatically.

Step 3 management: At discharge, schedule first follow-up within 1 week, provide written sick-day instructions (any fever ≥38.0 → ED), pharmacy review for drug interactions (azoles double CSA levels), and ensure 24/7 hematology contact number.

Follow-Up, Monitoring Parameters, and Counseling

— Weekly CBC, reticulocyte count, BMP, LFTs, magnesium, CSA trough for first 4–8 weeks

— Biweekly through month 3

— Monthly through month 12

— Bone marrow biopsy at 3 and 6 months to assess response and screen for clonal evolution

— Then every 6–12 months long-term, or with cytopenia changes

— 200–400 ng/mL during induction

— Dose-adjust for renal function, drug interactions

— Magnesium oxide PO as needed (CSA causes urinary wasting)

— LFTs weekly ×4, then biweekly ×3 months, then monthly

— Hold for ALT >3× ULN with bilirubin rise or symptoms

— Annual ophthalmologic exam (cataract risk with chronic use)

— Complete response: Hb >10, ANC >1000, platelets >100K

— Partial response: transfusion independence + improvement of ≥1 line beyond severity criteria

— No response: persistent SAA criteria → refer for transplant

— Annual bone marrow biopsy with cytogenetics for ≥10 years

— Flow cytometry for PNH clones annually

— Watch for evolution to MDS, AML, PNH (~10–15% over 10 years)

— Fever ≥38.0°C → immediate ED evaluation (carry written note)

— Avoid contact sports, NSAIDs, IM injections (bleeding risk)

— Pregnancy planning — reliable contraception; pregnancy can be safely managed with CSA but plan with hematology/MFM

— Fertility — discuss preservation before transplant

— Genetic counseling for inherited forms

— Anxiety/depression common; refer for counseling

— Support groups (Aplastic Anemia and MDS International Foundation)

— Financial counseling for transplant costs

— Pediatric to adult hematology transition starting age 14–18 with structured handoff

— Survivorship clinics post-transplant for late-effect surveillance

Monitoring schedule during IST:

Cyclosporine trough target:

Eltrombopag monitoring:

Response assessment criteria (at 3 and 6 months):

Long-term clonal surveillance:

Counseling topics:

Psychosocial support:

Transition of care:

Board pearl: Even after complete hematologic response, continue surveillance for life — clonal evolution to MDS/AML can occur decades later, particularly with monosomy 7 development.

Step 3 management: Use a written monitoring plan shared with PCP — close coordination prevents missed labs and unrecognized infections; PCP should not adjust immunosuppression without hematology input.

Ethical, Legal, and Patient Safety Considerations

— Patients must understand the trade-offs: HSCT offers cure but ~10–20% transplant-related mortality and lifelong GVHD risk; IST is less morbid acutely but doesn't cure stem cell defect, with relapse and clonal evolution risk

— In adolescents, consent vs assent: minors should participate meaningfully but parents/guardians provide legal consent

— Document discussion of fertility implications before any cytotoxic therapy

— When the matched sibling is a minor, careful ethical evaluation required — risks to donor must be minimized, donor advocate (separate from recipient's team) should be involved

— Cannot ethically conceive a "savior sibling" without comprehensive counseling; PGD-based selection is permissible with rigorous oversight

— Irradiation of cellular products is mandatory to prevent transfusion-associated GVHD — failure is a never-event

— Two-identifier verification at every transfusion to prevent ABO mismatch hemolytic reactions

— Avoid directed donations from family members in transplant candidates — alloimmunization may compromise future transplant

— If benzene or pesticide exposure identified → notify OSHA / occupational health; workers' compensation may apply

— Drug-induced AA from a prescribed medication → report to FDA MedWatch

— Discharge after ATG without clear follow-up appointment is a major safety gap — serum sickness peaks 7–14 days out

— Medication reconciliation critical: cyclosporine interacts with azoles, macrolides, statins, calcium channel blockers, grapefruit, St. John's wort

— PCP must be informed of immunosuppression — avoid live vaccines, screen for infections aggressively

— Genetic testing for inherited marrow failure has family implications — discuss disclosure with patient before testing siblings; respect autonomy of relatives

— Transplant requires significant insurance/financial resources; social work involvement early prevents access disparities

— Refractory AA with severe complications: discuss goals of care, palliative transfusion strategies, advance directives

— Patients have the right to decline transplant even if curative — respect autonomy after thorough counseling

Informed consent for IST vs HSCT:

Sibling donor ethics — pediatric donor consideration:

Patient safety / transfusion safety:

Mandatory reporting and occupational health:

Transition-of-care risks (high-yield Step 3 theme):

Confidentiality:

Resource allocation:

End-of-life considerations:

Board pearl: Transfusion-associated GVHD from non-irradiated products in an immunocompromised AA patient is nearly 100% fatal — irradiation of all cellular products is a non-negotiable patient safety standard.

Step 3 management: Before discharge after ATG, schedule a follow-up appointment within 7 days, provide written sick-day rules, perform pharmacist-led medication reconciliation, and ensure the patient has a 24-hour hematology contact.

High-Yield Associations and Rapid-Fire Clinical Facts

— Seronegative hepatitis → AA 2–6 months later, young men, poor prognosis

— Parvovirus B19 → pure red cell aplasia (not pancytopenia)

— EBV, HIV

— Fanconi: café-au-lait + thumb anomalies + short stature; diepoxybutane (DEB)/MMC chromosomal breakage test; AR

— Dyskeratosis congenita: nail dystrophy + oral leukoplakia + reticular pigmentation; telomere dysfunction

— Shwachman-Diamond: pancreatic insufficiency + neutropenia

— Diamond-Blackfan: pure red cell aplasia, craniofacial anomalies, triphalangeal thumbs

Most common cause of acquired AA: Idiopathic (~70%) — autoimmune T-cell mediated.

Drug class most classically associated: Chloramphenicol — both predictable dose-related and idiosyncratic.

Other classic drug culprits: carbamazepine, phenytoin, sulfonamides, gold, methimazole, NSAIDs (phenylbutazone), linezolid.

Toxin classic: Benzene exposure (dry cleaners, rubber, petroleum workers).

Viral classics:

Inherited syndromes:

Camitta severity criteria (SAA): marrow <25% cellular + 2 of 3: ANC <500, platelets <20K, retic <60K.

First-line for young SAA with MSD: Bone marrow HSCT (not peripheral blood).

First-line IST regimen: Horse ATG + cyclosporine + eltrombopag + short steroid taper.

Horse > rabbit ATG: Higher response (68% vs 37%) and survival in first-line SAA (NIH RCT).

Clonal evolution risk after IST: ~10–15% over 10 years — MDS, AML, PNH.

PNH clone in AA: Found in ~50%; small clones predict good IST response.

Cyclosporine trough target: 200–400 ng/mL; taper over ≥12 months to prevent relapse.

Eltrombopag absorption: Separate from antacids/calcium/iron by 4 hours.

Mandatory blood product modifications: Irradiated + leukoreduced + CMV-safe for all cellular products.

Avoid in potential transplant candidates: Family member blood donations (alloimmunization).

Pregnancy treatment: Cyclosporine + supportive transfusions; avoid ATG.

Fanconi conditioning: Fludarabine + LOW-dose cyclophosphamide; NO full-dose alkylators or TBI.

Telomere disorder treatment adjunct: Danazol (androgen) upregulates telomerase.

Splenomegaly + pancytopenia: NOT aplastic anemia — think MDS, myelofibrosis, hairy cell, hypersplenism, kala-azar.

Board pearl: A young patient with pancytopenia + macrocytosis + low retic + hypocellular marrow + normal cytogenetics + no dysplasia = acquired aplastic anemia. Order HLA typing on siblings today.

Board Question Stem Patterns

— Adolescent male presents with fatigue, petechiae, gingival bleeding 2–3 months after an episode of acute hepatitis with negative A/B/C serologies. CBC: pancytopenia. Retic low. Smear unremarkable. → Answer: bone marrow biopsy → aplastic anemia; next step HLA typing of siblings + transplant referral.

— Patient on carbamazepine (or chloramphenicol, methimazole, phenytoin) for several weeks develops pancytopenia. → Stop offending drug, marrow biopsy, supportive care; if SAA criteria met, IST or HSCT.

— Patient working in shoe factory, dry cleaning, or petroleum refinery (benzene) with pancytopenia. → Benzene-induced AA; document exposure, refer.

— Teenager with short stature, café-au-lait spots, absent thumbs and pancytopenia. → Fanconi anemia; order DEB/MMC chromosomal breakage test; avoid standard chemotherapy doses.

— Young adult with dystrophic nails, oral leukoplakia, reticular skin pigmentation + pancytopenia → dyskeratosis congenita; order telomere length.

— AA patient develops dark urine, abdominal pain, thrombosis (Budd-Chiari) → flow cytometry for CD55/CD59 deficiency (FLAER); treat with eculizumab.

— SAA patient just received horse ATG; 10 days later develops fever, rash, arthralgia → serum sickness; treat with corticosteroids.

— Patient on cyclosporine + azole develops creatinine rise → drug-drug interaction, reduce CSA dose.

— AA patient develops fever, rash, pancytopenia, hepatitis days after transfusion → transfusion-associated GVHD (preventable with irradiation).

— Newly diagnosed SAA, age 25, has a fully matched sibling → matched sibling HSCT with bone marrow source.

— Newly diagnosed SAA, age 25, no MSD → horse ATG + CSA + eltrombopag; refer for MUD search in parallel.

— SAA age 65, fit, no MSD → IST first-line.

— Pancytopenia + splenomegaly + monocytopenia → hairy cell leukemia (not AA).

— Pancytopenia + macrocytosis + hypersegmented neutrophils → B12 deficiency.

— Pancytopenia + recent bariatric surgery + sideroblastic features → copper deficiency.

Pattern 1 — Post-hepatitis AA:

Pattern 2 — Drug-induced AA:

Pattern 3 — Industrial exposure:

Pattern 4 — Inherited marrow failure:

Pattern 5 — PNH overlap:

Pattern 6 — Treatment-related question:

Pattern 7 — Transfusion question:

Pattern 8 — Best next step questions:

Pattern 9 — Mimic exclusion:

Board pearl: The single most common Step 3 "next step" answer in newly diagnosed SAA in a young patient with a matched sibling is referral for matched sibling allogeneic bone marrow transplant — IST is the wrong answer if a sibling donor is available and the patient is young.

One-Line Recap

Aplastic anemia is an immune-mediated hypocellular marrow failure syndrome diagnosed by pancytopenia plus a hypocellular bone marrow without dysplasia, blasts, fibrosis, or infiltrate, and managed by urgent severity-based triage to either matched sibling allogeneic HSCT (young patients with a donor) or triple immunosuppressive therapy with horse ATG + cyclosporine + eltrombopag, alongside lifelong transfusion support with irradiated/leukoreduced products and surveillance for clonal evolution to MDS, AML, or PNH.

Diagnostic core: Pancytopenia + low reticulocytes + hypocellular marrow (<25% cellularity) without dysplasia or blasts; always exclude PNH (flow FLAER), inherited syndromes (DEB/MMC for Fanconi, telomere length for DC), MDS (cytogenetics), nutritional deficiencies (B12, folate, copper), and viral causes (hepatitis, HIV, parvovirus).

Severity drives therapy (Camitta): SAA = marrow <25% + 2 of 3 (ANC <500, platelets <20K, retic <60K); VSAA adds ANC <200. Severe disease requires definitive therapy — supportive care alone has ~80% 1-year mortality.

Treatment algorithm: Age <50 with matched sibling → allogeneic bone marrow HSCT first-line (5-yr OS 80–90%); otherwise horse ATG + cyclosporine + eltrombopag triple IST with ~80% overall response and ~40% complete response; CSA tapered slowly over ≥12 months to prevent relapse; HSCT for IST failure or relapse.

Long-term must-knows: All cellular blood products irradiated + leukoreduced + CMV-safe for life; avoid family member donations in transplant candidates; surveillance for clonal evolution (MDS/AML/PNH) ~10–15% over 10 years; in Fanconi anemia, use reduced-intensity fludarabine-based conditioning (no full-dose alkylators or TBI); in telomere disorders, danazol is a uniquely effective adjunct.

Board pearl: The fastest path to long-term survival in a young SAA patient is early HLA typing of siblings at diagnosis and immediate transplant-center referral — every week of delay raises infection and bleeding mortality.