Blood & Lymphoreticular

Pure red cell aplasia: causes and management

Clinical Overview and When to Suspect Pure Red Cell Aplasia

— Adult with progressive fatigue, dyspnea, pallor and a low Hb with WBC and platelets normal, plus a reticulocyte count that is inappropriately low

— Patient with thymoma found to have anemia (10–15% of thymomas associate with PRCA)

— Patient with CLL, large granular lymphocyte (LGL) leukemia, or solid-organ/stem cell transplant developing isolated anemia

— Erythropoietin-treated CKD patient with sudden loss of response and transfusion dependence → suspect anti-EPO antibody PRCA

— Child with sickle cell or hereditary spherocytosis presenting with transient aplastic crisis (parvovirus B19)

— HIV patient on antiretrovirals with isolated anemia → think B19 persistence

— Acquired primary (idiopathic, autoimmune)

— Acquired secondary (thymoma, lymphoproliferative, viral, drugs, ABO-mismatched HSCT, pregnancy, anti-EPO antibodies)

— Congenital (Diamond–Blackfan anemia)

Board pearl: The triad that nails PRCA in a stem is (1) normocytic anemia, (2) reticulocytopenia, (3) normal WBC and platelets. If WBC or platelets are also low, you are dealing with aplastic anemia or MDS — not PRCA.

Step 3 management: Before chasing exotic causes, document the isolated cytopenia pattern with CBC + differential + reticulocyte count + peripheral smear, then commit to bone marrow biopsy. Do not transfuse reflexively without sending parvovirus B19 PCR first if recent viral prodrome — it changes treatment to IVIG, not immunosuppression.

Pure red cell aplasia (PRCA) = isolated normochromic, normocytic anemia with reticulocytopenia (<1% or <10,000/µL) and near-absent bone marrow erythroid precursors (<1%), with preserved myeloid and megakaryocytic lineages

Mechanism: selective failure of erythroid progenitor maturation (BFU-E and CFU-E), most often via immune-mediated destruction or direct viral cytotoxicity to erythroblasts

When to suspect on Step 3:

Classify as:

Presentation Patterns and Key History

— Progressive exertional dyspnea, fatigue, palpitations, headache, syncope, angina in older adults

— Often profound anemia (Hb 4–7 g/dL) at presentation because compensation has occurred slowly

— Days-to-weeks of pallor after a febrile/flu-like illness, slapped-cheek rash (children) or arthralgias (adults, especially women)

— In hemolytic anemia patients (sickle cell, HS, thalassemia, G6PD), B19 causes a transient aplastic crisis — sudden Hb drop with reticulocytopenia despite chronic hemolysis

— Medications: phenytoin, valproate, azathioprine, mycophenolate, isoniazid, chloramphenicol, sulfonamides, recombinant EPO (especially older subcutaneous epoetin-α formulations)

— Infections: parvovirus B19, EBV, HIV, hepatitis, HTLV-1, CMV

— Pregnancy (rare reversible PRCA, resolves postpartum)

— Prior malignancy: thymoma symptoms (chest pressure, myasthenic features), lymphadenopathy, B symptoms suggesting CLL/LGL/lymphoma

— Autoimmune disease: SLE, RA, autoimmune thyroid, IBD

— Transplant history: ABO-major-mismatched allogeneic HSCT is a classic Step 3 trigger

— Travel/exposures and sick contacts (pregnant teacher exposed to fifth disease)

Key distinction: B19-induced PRCA in an immunocompetent patient is self-limited (resolves with antibody formation in 2–4 weeks); in immunocompromised patients (HIV, post-transplant, chemo), B19 causes chronic/persistent PRCA because they cannot clear viremia — requires IVIG, not steroids.

Board pearl: Any stem mentioning "loss of response to erythropoietin with rising transfusion requirements in a CKD patient" = anti-EPO antibody PRCA until proven otherwise. Stop the ESA immediately; do not switch to another ESA (cross-reactivity).

Insidious onset (weeks to months) is typical for autoimmune and thymoma-associated PRCA

Acute onset suggests parvovirus B19 or drug-induced

Targeted history must capture:

Physical Exam Findings and Hemodynamic Assessment

— New angina, ST changes, troponin elevation = demand ischemia, admit

— Decompensated CHF (rales, S3, JVD, edema) from high-output failure in elderly

— Mental status changes from cerebral hypoperfusion

— Anterior mediastinal fullness, ptosis, fatigable weakness, diplopia → thymoma ± myasthenia gravis

— Cervical/axillary lymphadenopathy, splenomegaly → CLL, lymphoma, LGL leukemia

— Slapped cheek (children), lacy reticular rash, symmetric small-joint arthritis → parvovirus B19

— Malar rash, oral ulcers, serositis → SLE-associated PRCA

— Triphalangeal thumbs, short stature, craniofacial anomalies, cleft palate in a child → Diamond–Blackfan anemia

— Hyperpigmentation, café-au-lait, short stature → Fanconi (though usually pancytopenia)

CCS pearl: On a CCS case, after CBC confirms isolated anemia with reticulocytopenia, order in this sequence: peripheral smear → reticulocyte count → LDH, haptoglobin, bilirubin (rule out hemolysis) → B12/folate/iron studies → parvovirus B19 IgM/IgG and PCR → bone marrow biopsy → chest CT for thymoma. Advance the clock between results — do not stack orders unnecessarily.

Board pearl: A flow murmur and tachycardia with Hb 5 g/dL, reticulocytes 0.2%, normal WBC/platelets, and a mediastinal mass on CXR is a near-pathognomonic stem for thymoma-associated PRCA — answer is thymectomy plus immunosuppression.

General appearance: pallor of conjunctivae, palms, nail beds; in severe anemia, resting tachycardia, wide pulse pressure, flow murmur at left sternal border, bounding pulses

Vital signs: evaluate for high-output state — tachycardia >100, orthostasis, narrow SpO2 reserve on ambulation; hypotension is late

Hemodynamic decompensation signs that change disposition:

Targeted exam clues to etiology:

Absence of findings matters: no petechiae, no infections, no gum bleeding — distinguishes PRCA from aplastic anemia/MDS where all lines fail

Diagnostic Workup — Initial Labs, Imaging, Biomarkers

— Normocytic, normochromic anemia (MCV 80–100); macrocytosis can occur if reticulocytes ever rebound or with concurrent B12/folate deficiency

— Absolute reticulocyte count <10,000/µL (corrected retic <1%) is the defining finding

— WBC, neutrophils, lymphocytes, platelets all normal — confirm twice before labeling PRCA

— Smear: no schistocytes, no blasts, no dysplastic forms, no nucleated RBCs

— LDH, indirect bilirubin, haptoglobin, direct Coombs (DAT)

— Parvovirus B19 IgM, IgG, and quantitative PCR (PCR is essential in immunocompromised — antibodies may be absent)

— HIV, hepatitis B/C, EBV, CMV

— Chest CT with contrast is mandatory to evaluate for thymoma in any adult with newly diagnosed PRCA — CXR misses small thymomas

— Consider abdominal imaging if lymphoma/CLL suspected

Step 3 management: Do not skip the chest CT — missing a thymoma changes the entire treatment paradigm (thymectomy is curative or strongly disease-modifying in 30–40% of thymoma-associated PRCA). This is a frequent exam trap when the question gives a "normal CXR."

Board pearl: Reticulocyte index = reticulocyte % × (Hct/45) × (1/maturation factor). In PRCA the uncorrected retic is already near zero, so you don't need the formula — but Step 3 loves to test that reticulocytopenia + isolated anemia = production failure, not loss or destruction.

CBC with differential + reticulocyte count + peripheral smear are the cornerstone

Hemolysis panel to exclude brisk hemolysis with marrow suppression overlay:

Iron studies, B12, folate, TSH, creatinine, LFTs — exclude nutritional and endocrine mimics

Viral serologies/PCR:

Autoimmune screen: ANA, RF; consider anti-dsDNA if SLE suspected

Imaging:

Flow cytometry of peripheral blood to screen for LGL leukemia (CD3+CD8+CD57+ expansion) and CLL

EPO level: elevated in true PRCA (appropriate response to anemia); if low or anti-EPO antibody suspected, send specific anti-EPO antibody assay

Diagnostic Workup — Advanced and Confirmatory Studies

— Findings: normocellular or mildly hypocellular marrow with erythroid precursors <1% (or <5% with maturation arrest at the proerythroblast stage), normal myeloid and megakaryocytic lineages, normal M:E ratio inverted (markedly elevated due to absent erythroids)

— Giant pronormoblasts with intranuclear viral inclusions ("lantern cells") = pathognomonic for parvovirus B19

— Lymphoid aggregates → suggests CLL, LGL, or thymoma-associated

— Dysplasia, ring sideroblasts, blasts → think MDS, not PRCA

— Hypocellular marrow with trilineage failure → aplastic anemia

Key distinction: PRCA vs aplastic anemia vs MDS vs myelophthisis — all can present with anemia, but PRCA uniquely shows isolated erythroid failure with preserved other lineages on marrow biopsy. MDS shows dysplasia; aplastic shows trilineage hypocellularity; myelophthisis shows leukoerythroblastic smear (teardrops, nucleated RBCs, left-shifted myeloid).

Board pearl: Giant pronormoblasts on marrow + arthralgia in a young woman + reticulocytopenia = parvovirus B19. Treatment is supportive if immunocompetent; IVIG 0.4 g/kg/day × 5–10 days if immunocompromised or persistent.

Bone marrow aspirate and biopsy is required to confirm PRCA and exclude mimics

Cytogenetics and FISH on marrow: rule out 5q–, del(7), trisomy 8 (MDS); JAK2 if suspecting MPN

Flow cytometry of marrow: clonal T-cell populations (LGL), B-cell clones (CLL)

T-cell receptor (TCR) gene rearrangement studies if LGL leukemia suspected — STAT3 mutation analysis is increasingly used

Anti-erythropoietin antibody testing in any ESA-treated patient with new PRCA — neutralizing antibodies confirm the diagnosis; sample must be drawn before stopping the ESA ideally

Quantitative parvovirus B19 PCR in immunocompromised; serology alone is unreliable

HLA typing and chimerism studies in post-HSCT PRCA from ABO mismatch

Genetic testing for RPS19, RPL5, RPL11 and other ribosomal protein genes in suspected Diamond–Blackfan anemia; adenosine deaminase (eADA) is elevated in DBA RBCs

Risk Stratification and First-Line Management Logic

— Parvovirus B19 + immunocompetent → supportive transfusions, expect spontaneous recovery as IgG develops

— Parvovirus B19 + immunocompromised → IVIG; in HIV, also optimize ART

— Drug-induced → discontinue offending agent; recovery in weeks

— Thymoma → thymectomy (only ~30–40% remit with surgery alone — most still need immunosuppression)

— Anti-EPO antibody PRCA → stop ESA permanently, do not substitute; immunosuppression (cyclosporine, steroids) ± rituximab; consider renal transplant

— CLL/lymphoma-associated → treat the underlying lymphoproliferative disease

— LGL leukemia → methotrexate, cyclophosphamide, or cyclosporine

— ABO-mismatched HSCT PRCA → taper immunosuppression, donor lymphocyte infusion, rituximab, plasma exchange, or erythropoietin

— Idiopathic acquired PRCA → immunosuppression (cyclosporine first-line)

— Maintain Hb ~7–8 g/dL (higher if symptomatic, CAD, elderly)

— Leukoreduced, irradiated in transplant or candidates for transplant

— Watch for iron overload with chronic transfusion — start chelation after ~20 units or ferritin >1000

Step 3 management: In an outpatient with newly diagnosed idiopathic PRCA and Hb 8.5 g/dL, no cardiac symptoms — start cyclosporine with target trough 150–250 ng/mL and follow CBC weekly; transfuse only if symptomatic or Hb <7. Do not jump to combination immunosuppression upfront.

Board pearl: Cyclosporine (response ~65–75%) is first-line for idiopathic acquired PRCA, outperforming corticosteroids alone. Add prednisone if no response by 12 weeks; consider rituximab or cyclophosphamide if refractory.

Step 1: Identify and treat the underlying cause — PRCA is rarely truly idiopathic; ~50% have an identifiable trigger

Algorithm:

Transfusion strategy during workup:

Severity markers: Hb <6 g/dL, transfusion-dependent, evidence of end-organ ischemia → escalate urgency of immunosuppression

Pharmacotherapy — First-Line Drug Regimen

— Dose: 3–6 mg/kg/day divided BID, target trough level 150–250 ng/mL

— Onset of erythroid response: 6–12 weeks; continue at least 3 months before declaring failure

— Once Hb normalizes, taper slowly over months; relapse common, may need indefinite low-dose maintenance

— Monitoring: BP, Cr, K+, Mg2+, LFTs, lipids, glucose every 2–4 weeks initially; drug levels weekly until stable

— Adverse effects: nephrotoxicity, hypertension, hyperkalemia, hypomagnesemia, gum hyperplasia, hirsutism, tremor, increased malignancy risk

— Drug interactions: CYP3A4 — azoles, macrolides, diltiazem raise levels; rifampin, phenytoin lower levels; statins (avoid simvastatin/lovastatin)

— Prednisone 1 mg/kg/day with taper over 3 months; response rate ~30–40% as monotherapy, often combined with CsA

— Add PJP prophylaxis (TMP-SMX), calcium/vitamin D, PPI, glucose monitoring

— 0.4 g/kg/day × 5 days (total 2 g/kg); may repeat if relapse; check IgA before infusion in IgA-deficient patients

— Monitor for aseptic meningitis, renal injury (especially sucrose-containing formulations), thrombosis

— 375 mg/m² weekly × 4 doses; screen for HBV before use; monitor for infusion reactions, prolonged B-cell aplasia

Board pearl: A patient on cyclosporine with new creatinine rise needs dose reduction, not discontinuation — abrupt stop risks flare. Always check a trough level and review interacting drugs (started a "Z-pack"? azole for thrush?) before adjusting.

Step 3 management: Document baseline BP, Cr, lipids, and pregnancy test before starting CsA, and counsel about live vaccine avoidance and skin cancer screening.

Cyclosporine A (CsA) — first-line for idiopathic acquired PRCA

Corticosteroids — adjunct or alternative

IVIG — specifically for parvovirus B19 PRCA

Rituximab — second-line or for CLL/post-HSCT PRCA

Cyclophosphamide — refractory cases: 50–100 mg PO daily or pulse IV; watch for cytopenias, hemorrhagic cystitis, infertility, secondary malignancy

Erythropoiesis-stimulating agents — contraindicated in anti-EPO antibody PRCA; otherwise generally ineffective in PRCA because the problem is downstream of EPO

Procedures and Expanded Pharmacology

— Indicated for any thymoma, regardless of PRCA response, due to malignancy risk

— Hematologic remission after thymectomy alone: ~30–40%; most patients still require post-op immunosuppression (CsA ± steroids)

— Preoperative workup: chest CT, PFTs, anti-AChR antibody (myasthenia screen — affects anesthesia plan)

— Approaches: median sternotomy (classic), VATS, robotic; complete resection (R0) is the goal

— Used for ABO-mismatched allogeneic HSCT PRCA to remove recipient anti-donor isohemagglutinins

— Adjunct in refractory anti-EPO antibody PRCA

— Add prednisone to CsA → switch/add rituximab → cyclophosphamide → alemtuzumab (anti-CD52, especially for T-LGL–associated) → antithymocyte globulin (ATG) → eltrombopag (emerging evidence in refractory disease)

— Daratumumab has shown activity in post-HSCT and refractory antibody-mediated PRCA

— pRBCs to maintain Hb ~8 g/dL

— Iron chelation (deferasirox or deferoxamine) once ferritin >1000 ng/mL or ≥20 units transfused

— Hepatitis B vaccination; CMV-negative or leukoreduced products in immunocompromised

CCS pearl: When thymoma is found on chest CT in a PRCA case, the order set is: thoracic surgery consult → PFTs → anti-AChR antibody → CT-guided biopsy not required for resectable mass → schedule thymectomy → continue transfusion support and start cyclosporine bridge. Advance the clock to post-op and reassess reticulocyte count at 4–6 weeks.

Board pearl: Eltrombopag, a TPO mimetic, paradoxically stimulates trilineage hematopoiesis and is being used in refractory acquired PRCA — know it as "salvage in refractory cases."

Thymectomy

Plasmapheresis

Donor lymphocyte infusion (DLI) for post-HSCT PRCA refractory to immunosuppression taper

Stem cell transplant — rarely for Diamond–Blackfan anemia unresponsive to steroids and transfusion-dependent; HLA-matched sibling preferred

Refractory/relapsed pharmacology ladder:

Chronic transfusion support:

Splenectomy has minimal role in PRCA (unlike AIHA)

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher prevalence of thymoma-associated, LGL-associated, and MDS-overlap PRCA — biopsy threshold should be low

— Tolerate anemia less well: more likely to develop demand ischemia, decompensated CHF, falls, delirium at moderate Hb levels

— Maintain Hb target ~8 g/dL or even 9 if symptomatic CAD; do not over-transfuse (TACO risk)

— Cyclosporine dose reduction by 25–50% expected due to age-related decline in GFR; check trough more frequently

— Polypharmacy increases CsA interaction risk — review every medication including OTC (St. John's wort lowers levels)

— Screen for occult MDS with cytogenetics — PRCA can be a presenting feature of low-grade MDS in older adults

— Anti-EPO antibody PRCA is the must-know scenario — typically after >6 months of subcutaneous epoetin; stop ESA permanently; switching ESAs is contraindicated due to antibody cross-reactivity

— Peginesatide historically considered (no antibody cross-reactivity) — withdrawn from market; modern approach uses immunosuppression + transfusions; renal transplant is curative

— Cyclosporine dose by lean body weight; target lower trough (100–200) due to additive nephrotoxicity

— Avoid NSAIDs, aminoglycosides, IV contrast where possible during CsA therapy

— CsA is hepatically metabolized — reduce dose 25–50% in Child-Pugh B/C, monitor levels closely

— Cyclophosphamide requires hepatic activation; dose-adjust and monitor LFTs

— Avoid azathioprine in TPMT-deficient patients (genotype before use)

Key distinction: A CKD patient on epoetin-α with rising transfusion needs, undetectable reticulocytes, and a previously stable Hb = anti-EPO antibody PRCA, not "ESA hyporesponse from iron deficiency or inflammation." Send anti-EPO antibodies, stop the ESA, refer to hematology, and consider renal transplantation as definitive therapy.

Step 3 management: Document baseline GFR and re-check in 2 weeks after starting CsA in any elderly or CKD patient; >25% Cr rise → dose reduce.

Elderly (>65) considerations:

Chronic kidney disease:

Hepatic impairment:

Special Populations — Pregnancy and Pediatrics

— Rare pregnancy-associated PRCA described — often resolves spontaneously postpartum

— Parvovirus B19 in pregnancy is critical: maternal infection → transplacental transmission → fetal anemia, hydrops fetalis, intrauterine death, especially in second trimester

— Management: serial MCA-PSV Doppler for fetal anemia; intrauterine transfusion if anemia severe; IVIG for symptomatic maternal disease

— Cyclosporine is category C but used in transplant pregnancies with acceptable outcomes; corticosteroids preferred when immunosuppression needed

— Avoid: cyclophosphamide (teratogenic, especially first trimester), methotrexate, mycophenolate, rituximab if avoidable

— Diamond–Blackfan anemia (DBA):

— Congenital, autosomal dominant in most; ribosomal protein gene mutations (RPS19 most common)

— Presents in first year of life with macrocytic anemia, reticulocytopenia, elevated eADA and HbF

— Associated anomalies: triphalangeal thumbs, short stature, craniofacial defects, cardiac/GU anomalies; increased risk of MDS/AML and solid tumors

— Treatment: corticosteroids (response ~80%), chronic transfusion + chelation if steroid-refractory, HSCT is curative for transfusion-dependent cases

— Transient erythroblastopenia of childhood (TEC):

— Acquired, age 1–4 years, post-viral, normocytic anemia, self-resolves in 1–2 months; no treatment needed

— Key distinction from DBA: TEC = older child, normocytic, normal eADA, normal HbF, no congenital anomalies, resolves spontaneously

— Parvovirus B19 transient aplastic crisis in children with sickle cell — sudden Hb drop, transfuse, isolate (droplet precautions in hospital)

Board pearl: Macrocytic anemia + reticulocytopenia + thumb anomaly in an infant = Diamond–Blackfan; normocytic anemia + reticulocytopenia + 2-year-old recovering from a cold = TEC. Step 3 loves this pair.

Step 3 management: In any pregnant patient with PRCA, coordinate hematology + MFM, and avoid teratogens; in pediatric DBA, refer early for HLA typing of siblings.

Pregnancy:

Pediatrics:

Complications and Adverse Outcomes

— High-output cardiac failure, especially in elderly with baseline CAD/HF

— Demand ischemia, MI, arrhythmias

— Cerebral hypoperfusion — TIA-like symptoms, syncope, falls

— Growth failure and developmental delay in untreated pediatric cases

— Iron overload → hepatic fibrosis, cardiomyopathy (restrictive then dilated), endocrinopathy (diabetes, hypogonadism, hypothyroidism, hypoparathyroidism); monitor ferritin, T2* cardiac MRI

— Alloimmunization → difficulty cross-matching, delayed hemolytic transfusion reactions

— Transfusion-transmitted infection (small but nonzero)

— TACO, TRALI

— Cyclosporine: nephrotoxicity, hypertension, neurotoxicity (tremor, seizures, PRES), gingival hyperplasia, hirsutism, hyperkalemia, hypomagnesemia, skin cancers, lymphoma, opportunistic infections

— Corticosteroids: hyperglycemia/steroid-induced diabetes, osteoporosis, AVN, cataracts, mood changes, immunosuppression, adrenal suppression on taper

— Rituximab: infusion reactions, HBV reactivation (screen and prophylax), late neutropenia, PML (rare)

— Cyclophosphamide: hemorrhagic cystitis (use mesna with high doses), infertility, secondary AML/MDS, bladder cancer

— Acquired idiopathic PRCA can evolve into aplastic anemia or MDS — repeat marrow if cytopenias broaden

— DBA carries lifetime risk of MDS, AML, osteosarcoma, colon cancer

Board pearl: A transfusion-dependent PRCA patient with new heart failure and bronze skin — think transfusional hemochromatosis. Check ferritin and start deferasirox (oral, once daily, monitor renal/hepatic function).

Step 3 management: Every patient on chronic immunosuppression needs PJP prophylaxis (TMP-SMX), age-appropriate cancer screening, dermatology surveillance, vaccinations (inactivated only), and bone health assessment.

Anemia-related complications:

Transfusion-related complications:

Immunosuppression-related complications:

Disease evolution:

Relapse: common with CsA taper — most patients require maintenance therapy

When to Escalate Care — ICU, Consult, Inpatient

— Symptomatic anemia (angina, dyspnea at rest, syncope, new HF) regardless of Hb

— Hb <6 g/dL even if asymptomatic in older or comorbid patients

— New diagnosis of PRCA requiring expedited workup including bone marrow biopsy and chest CT

— Suspected parvovirus B19 in immunocompromised host needing IVIG

— Initiation of high-dose immunosuppression in patients unable to manage outpatient monitoring

— Hemodynamic instability, demand MI with ischemic ECG changes, decompensated high-output HF requiring pressors or BiPAP

— Massive transfusion requirements

— Severe transfusion reactions

— Sepsis on immunosuppression

— Hematology/oncology — should be the primary coordinator for any new PRCA

— Cardiothoracic surgery for any thymoma

— Nephrology if anti-EPO antibody PRCA or CKD

— Infectious disease for chronic B19, HIV-related, or post-transplant PRCA

— Transfusion medicine for chronic transfusion strategy, alloimmunized patients, ABO-mismatched HSCT cases

— Bone marrow transplant team for DBA or refractory severe acquired PRCA

— MFM if pregnant

— Stable Hb ≥7–8 g/dL, asymptomatic, no end-organ ischemia

— Reliable follow-up and ability to obtain weekly labs

— No suspicion of acute infection or marrow failure beyond PRCA

CCS pearl: On CCS, after the bone marrow confirms PRCA and chest CT shows a 4-cm anterior mediastinal mass, change location to inpatient or scheduled OR, consult CT surgery, order PFTs and anti-AChR antibody, and continue transfusion to keep Hb >8 perioperatively. Advance the clock to postop day 1.

Board pearl: A new PRCA diagnosis with Hb 4.5 g/dL and chest pain is an admission, telemetry, type and cross 2 units, troponin, ECG — not an outpatient workup.

Admit (inpatient ward) for:

ICU triage for:

Consults to obtain:

Outpatient management is appropriate when:

Key Differentials — Same-Category (Marrow Failure / Anemia of Production)

— Trilineage cytopenia (anemia + neutropenia + thrombocytopenia) with hypocellular marrow

— Causes: idiopathic, hepatitis-associated, drugs (chloramphenicol, gold, NSAIDs), benzene, radiation

— Treatment: ATG + cyclosporine + eltrombopag; HSCT in young severe cases

— Cytopenia(s) with marrow dysplasia, often macrocytic anemia, ring sideroblasts; cytogenetics positive (5q–, –7, +8)

— Can present as "PRCA-like" with isolated anemia, especially MDS with 5q deletion (lenalidomide-responsive)

— Pancytopenia with leukoerythroblastic smear (teardrops, nucleated RBCs, immature myeloid forms), blasts

— Macrocytic, hypersegmented neutrophils, mildly low reticulocytes, often mild leukopenia/thrombocytopenia

— Marrow shows megaloblastic erythroid hyperplasia — opposite of PRCA

— Normocytic, normochromic, low/normal reticulocytes, high ferritin, low TIBC, low transferrin saturation, elevated hepcidin

— Marrow is not erythroid-empty — distinguishes from PRCA

— Microcytic, high RDW, low ferritin, high TIBC, low transferrin saturation; reticulocytes are low but rise with iron repletion

— Low EPO production; responds to ESAs; if no response → think anti-EPO antibody PRCA

Key distinction: PRCA = isolated erythroid failure with preserved WBC and platelets and normal marrow myeloid/megakaryocytic lineages. Any deviation from "only RBCs affected" should push you to aplastic anemia, MDS, or myelophthisis.

Board pearl: Macrocytic anemia + low retics + hypersegmented neutrophils = B12 deficiency, not PRCA. Macrocytic anemia + low retics + congenital anomalies in infant = Diamond–Blackfan. Macrocytic anemia + low retics + 5q deletion = MDS.

Aplastic anemia:

Myelodysplastic syndrome (MDS):

Acute leukemia / myelophthisis:

Megaloblastic anemia (B12/folate):

Anemia of chronic disease/inflammation:

Iron deficiency anemia:

Anemia of CKD:

Key Differentials — Other-Category Causes of Reticulocytopenia/Anemia

— Chronic hemolysis (sickle cell, HS, thalassemia, AIHA) usually shows elevated reticulocytes; sudden drop with reticulocytopenia in this setting = parvovirus B19 aplastic crisis

— Anemia + reticulocytosis + positive DAT, elevated LDH/indirect bilirubin, low haptoglobin — opposite reticulocyte pattern from PRCA

— Schistocytes on smear, thrombocytopenia, AKI/neuro/fever — multilineage involvement, not PRCA

— Mild normocytic or macrocytic anemia, low reticulocytes; always check TSH in unexplained anemia

— Anemia from reduced erythropoietic drive; cortisol and ACTH testing in unexplained normocytic anemia with hypotension/hyponatremia

— Reticulocytes take 3–5 days to rise; an early bleeding patient can appear "reticulocytopenic" — history of bleeding clarifies

— Linezolid, valganciclovir, zidovudine, chemotherapy — often multilineage; isolated red cell suppression more typical of phenytoin, isoniazid, MMF

— Macrocytic anemia + neutropenia + neurologic symptoms; underdiagnosed; check serum copper and ceruloplasmin in bariatric or excess-zinc-supplement patients

— Multifactorial: zidovudine, opportunistic infection, B19 persistence, lymphoma; check HIV in any unexplained PRCA

Step 3 management: Always send TSH, B12, folate, iron studies, retic count, peripheral smear, HIV, hepatitis serologies, ANA before labeling anemia idiopathic — and never call it PRCA without a bone marrow biopsy demonstrating isolated erythroid hypoplasia.

Board pearl: A bariatric surgery patient with macrocytic anemia, neutropenia, and gait ataxia — think copper deficiency, not PRCA. Reverse with oral copper.

Hemolytic anemia with transient marrow suppression:

Autoimmune hemolytic anemia (warm and cold):

Microangiopathic hemolytic anemia (TTP, HUS, DIC, HELLP):

Hypothyroidism:

Hypopituitarism / adrenal insufficiency:

Acute blood loss (early):

Drug-induced bone marrow toxicity:

Copper deficiency / zinc excess:

HIV-associated anemia:

Secondary Prevention, Discharge Plan, and Long-Term Management

— Cyclosporine with explicit dosing schedule, target trough range, and lab order set

— Prednisone with detailed taper plan if started

— PJP prophylaxis (TMP-SMX single-strength daily or DS 3×/week) for any patient on combined immunosuppression or steroid >20 mg/day for >4 weeks

— Calcium 1200 mg + vitamin D 800–1000 IU for any patient on steroids

— PPI for steroid-related GI prophylaxis if comorbid risk

— Antihypertensive (often amlodipine — fewer CsA interactions than diltiazem) if CsA-induced HTN

— Folic acid 1 mg daily for chronic transfusion patients

— Iron chelator if ferritin >1000 or ≥20 units transfused

— Avoid NSAIDs, St. John's wort, grapefruit juice with CsA

— Stop any culprit drug; document allergy/intolerance in the chart

— Counsel on parvovirus B19 transmission (droplet) and avoidance during outbreaks if immunocompromised

— Sun protection and dermatology surveillance on long-term immunosuppression

— Inactivated influenza annually, pneumococcal (PCV20 or PCV15→PPSV23), HBV, shingles (Shingrix, recombinant — safe on immunosuppression), COVID-19

— Avoid live vaccines (MMR, varicella, yellow fever, live zoster, BAFF/intranasal flu) on immunosuppression

— Vaccinate before starting rituximab if possible (poor response after)

— Age-appropriate screening with attention to skin (annual derm), cervical (HPV), and any DBA-specific surveillance (colonoscopy starting age 35, osteosarcoma awareness)

Step 3 management: Reconcile medications at discharge; explicitly write that ESAs are contraindicated permanently in anti-EPO antibody PRCA — this prevents a downstream re-exposure error during a future renal admission.

Board pearl: Shingrix is recombinant and safe in immunosuppressed adults; Zostavax (live) is contraindicated.

Discharge medication checklist for PRCA:

Avoidance counseling:

Vaccinations:

Cancer screening:

Long-term monitoring for evolution to MDS/AML — repeat marrow if new cytopenias emerge

Follow-Up, Monitoring, and Counseling

— Weekly CBC + retic count until Hb stable for 4 weeks, then every 2–4 weeks

— CsA trough level weekly until therapeutic and stable, then monthly

— BMP (Cr, K, Mg), LFTs, BP every 2 weeks initially, then monthly

— Lipid panel and glucose at baseline and every 3 months

— Complete response: Hb normalization, transfusion independence, retic recovery

— Partial response: ≥2 g/dL Hb rise or 50% reduction in transfusion need

— No response by 12 weeks → reassess diagnosis, escalate therapy

— Adherence is critical — missing CsA doses risks rejection of remission

— Symptoms warranting urgent contact: fever, new bleeding, severe fatigue, chest pain, syncope, oliguria, jaundice

— Pregnancy planning: discuss with hematology before conception; some agents must be stopped/swapped

— Driving/work safety during severe anemia

— No raw or undercooked foods (immunosuppression — listeria, salmonella risk)

— Hand hygiene, mask in high-risk settings

— Avoid construction/soil exposure (aspergillus, histoplasma) on high-dose immunosuppression

Step 3 management: At every visit, calculate corrected reticulocyte count and trend it — the earliest sign of response or relapse is in the reticulocyte count, often before Hb changes.

Board pearl: A patient with PRCA in remission on low-dose CsA who develops gum bleeding and tremor — check CsA level (likely supratherapeutic from a new drug interaction).

Initial follow-up cadence after starting cyclosporine:

Response definitions:

Monitoring for relapse: every 3 months CBC + retic for first 2 years, then every 6 months indefinitely — relapse rate is 50%+ with CsA taper

Iron monitoring: ferritin every 3 months in transfusion-dependent; cardiac T2* MRI annually if ferritin >1000 or chronic transfusion >2 years

Counseling points:

Lifestyle:

Mental health screening — chronic illness, fatigue, body image (hirsutism from CsA, weight gain from steroids) impact QoL

Ethical, Legal, and Patient Safety Considerations

— Discuss infection risk, malignancy risk (especially skin cancers and lymphoma), infertility (cyclophosphamide), teratogenicity, and uncertain treatment duration

— In adolescents with DBA contemplating HSCT, ensure age-appropriate assent alongside parental consent and discuss fertility preservation before conditioning

— Many will refuse RBC transfusions; document precisely which products are acceptable (e.g., some accept albumin, EPO, IV iron, recombinant clotting factors)

— Aggressive optimization: parenteral iron, B12/folate, hematopoietic support; prompt immunosuppression is even more critical to avoid transfusion need

— Address advance directives and surrogate decision-making clearly; respect autonomy even when refusing transfusion is medically suboptimal

— Anti-EPO antibody PRCA: ensure the EHR allergy/intolerance list flags ESAs to prevent re-administration during future hospitalizations or by a covering nephrologist

— Communicate cyclosporine interactions explicitly at discharge; medication reconciliation must catch any new fluconazole, azithromycin, or statin

— Coordinate hematology, primary care, and (if applicable) nephrology, transplant, and oncology — designate a clear "PRCA captain"

— Parvovirus B19 in a pregnant healthcare worker — counsel about workplace exposure; not nationally reportable but trigger occupational health

— HIV diagnosis discovered during PRCA workup — confidential partner notification per state law

— Verify CMV-safe and irradiated blood products in transplant candidates and post-transplant patients — irradiation prevents transfusion-associated GVHD

— Double-check blood type and antibody screen in chronic transfusion patients (alloimmunization)

— Counsel about medication-induced PRCA: provide a written list of culprit drugs to share with future providers

Step 3 management: When a patient with anti-EPO antibody PRCA is later admitted for an unrelated reason and the inpatient team reflexively orders darbepoetin for low Hb, the outpatient nephrologist's clear discharge documentation prevents harm — this is the kind of transition-of-care failure Step 3 tests.

Board pearl: Irradiate blood products in any candidate for HSCT to prevent transfusion-associated GVHD — a near-uniformly fatal complication.

Informed consent for immunosuppression:

Jehovah's Witness patients:

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

Mandatory reporting and public health:

Patient safety:

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: "Giant pronormoblasts on marrow" + "arthralgia in adult woman" or "aplastic crisis in sickle cell" = parvovirus B19, every time.

Key distinction: PRCA = erythroid-only; aplastic anemia = trilineage; MDS = dysplasia.

Thymoma ↔ PRCA in ~5–15% of thymomas; conversely 10–15% of PRCA cases have thymoma

CLL ↔ PRCA — both autoimmune and direct mechanisms; rituximab effective

LGL leukemia ↔ PRCA in 8–20%; STAT3 mutations; methotrexate first-line

Parvovirus B19 ↔ giant pronormoblasts ("lantern cells"), arthralgia in adult women, slapped cheek in kids, hydrops in fetus, aplastic crisis in hemolytic disease, persistent infection in immunocompromised → IVIG

Diamond–Blackfan anemia ↔ ribosomal protein mutations (RPS19), triphalangeal thumbs, elevated eADA, elevated HbF, steroid-responsive

Transient erythroblastopenia of childhood ↔ ages 1–4, post-viral, normocytic, normal eADA, self-resolves

Anti-EPO antibody PRCA ↔ subcutaneous epoetin in CKD, antibody cross-reactivity (do not switch ESAs)

ABO-major-mismatched allogeneic HSCT ↔ delayed engraftment of red cells, persistent recipient isohemagglutinins

Drugs causing PRCA: phenytoin, valproate, azathioprine, MMF, isoniazid, chloramphenicol, sulfonamides, recombinant EPO

First-line idiopathic acquired PRCA: cyclosporine (response 65–75%)

Refractory salvage: rituximab, cyclophosphamide, ATG, alemtuzumab, eltrombopag, daratumumab

Marrow finding: erythroid precursors <1%, normal myeloid and megakaryocytic lineages

Lab triad: normocytic anemia + reticulocyte <1% + normal WBC/platelets

Iron overload threshold to chelate: ferritin >1000 or ≥20 units transfused

Pregnancy + parvovirus: MCA-PSV Doppler, possible intrauterine transfusion

PRCA in HIV: think persistent B19; treat with IVIG and ART

PRCA can evolve into: aplastic anemia, MDS, AML — re-biopsy if cytopenias broaden

Board Question Stem Patterns

— Answer: chest CT → thymoma → thymectomy + cyclosporine

— Answer: parvovirus B19 — supportive care if immunocompetent (self-limited)

— Answer: parvovirus B19 aplastic crisis → transfuse, droplet isolation, no immunosuppression needed

— Answer: anti-EPO antibody PRCA → stop ESA permanently (do not substitute another ESA), send anti-EPO antibody, start immunosuppression, consider transplant

— Answer: chronic parvovirus B19 → IVIG, optimize ART

— Answer: Diamond–Blackfan anemia → corticosteroids

— Answer: TEC → observation, self-resolves

— Answer: ABO-mismatched HSCT PRCA → taper immunosuppression, rituximab/plasma exchange

— Answer: LGL leukemia → methotrexate or cyclophosphamide

— Answer: cyclosporine (response ~70%), monitor trough 150–250, Cr, BP

Step 3 management: Recognize the trigger word first ("thymoma," "epoetin," "sickle cell + parvo," "post-transplant ABO mismatch," "triphalangeal thumb"), then commit to the etiology-specific therapy — Step 3 rewards mechanism-based action.

Board pearl: When in doubt and the stem is "idiopathic acquired adult PRCA," the answer is cyclosporine.

Stem 1: 65-year-old with progressive fatigue, Hb 6.2, MCV 88, retics 0.3%, normal WBC and platelets, CXR shows widened mediastinum

Stem 2: 28-year-old woman, schoolteacher, with 2 weeks of arthralgia, malar flush, then pallor. Hb 7.5, retics 0.5%, WBC and platelets normal. Marrow with giant pronormoblasts

Stem 3: Sickle cell patient with baseline Hb 8 now 4.2, retics 0.4%, fever, slapped-cheek appearance

Stem 4: CKD patient on subcutaneous epoetin for 14 months with rising transfusion requirements, Hb 5.8, retics undetectable

Stem 5: HIV patient with CD4 50, anemia, retic 0.2%, marrow with giant pronormoblasts

Stem 6: 9-month-old with pallor, triphalangeal thumbs, MCV 105, retics 0.1%, elevated eADA and HbF

Stem 7: 3-year-old recovering from URI now with pallor, Hb 6, MCV 78, retic 0.4%, no anomalies

Stem 8: Post–allogeneic HSCT (donor O+, recipient A+) with persistent anemia day +60, retic 0.3%, normal counts otherwise

Stem 9: Refractory PRCA on CsA + prednisone, T-cell flow shows CD3+CD8+CD57+ clone

Stem 10: Idiopathic acquired PRCA, first-line therapy?

One-Line Recap

Pure red cell aplasia is an isolated normocytic anemia with reticulocytopenia, preserved WBCs and platelets, and an erythroid-empty marrow whose management hinges on identifying the cause — parvovirus B19 (IVIG if immunocompromised), thymoma (thymectomy), drug or anti-EPO antibody (stop the agent), CLL/LGL (treat the clone) — with cyclosporine as first-line for idiopathic acquired disease.

Board pearl: If the stem gives you isolated anemia + reticulocytopenia + normal other lines, your reflex should be: smear → retic → B19 PCR → chest CT → bone marrow biopsy → cause-directed therapy, with cyclosporine as the default when nothing else fits.

Step 3 management: PRCA is a marathon — pick the right first-line agent, monitor closely, anticipate relapse, and integrate transitions of care to prevent harmful re-exposures.

Diagnostic triad: normocytic anemia + retic <1% + normal WBC/platelets, confirmed by marrow showing erythroid precursors <1% with preserved other lineages

Top causes to remember in order: parvovirus B19, thymoma, drugs, CLL/LGL leukemia, anti-EPO antibodies, ABO-mismatched HSCT, Diamond–Blackfan (peds), idiopathic

First-line treatments by cause: B19 immunocompromised → IVIG; thymoma → thymectomy + CsA; drug-induced → stop drug; anti-EPO → stop ESA permanently + immunosuppression; idiopathic acquired → cyclosporine 3–6 mg/kg/day, trough 150–250; DBA → corticosteroids; TEC → observation

Step 3 traps: don't switch ESAs in anti-EPO antibody PRCA; don't miss thymoma (always chest CT, not just CXR); don't give immunosuppression to immunocompetent B19 (self-limited); irradiate blood products in transplant candidates; document medication culprits to prevent re-exposure

Long-term plan: weekly labs initially, monitor for iron overload (chelate if ferritin >1000), watch for evolution to aplastic anemia or MDS, age-appropriate cancer screening, vaccinate (inactivated/recombinant only)