Pediatrics (System-Integrated)

Henoch-Schonlein purpura (IgA vasculitis)

Clinical Overview and When to Suspect IgA Vasculitis (HSP)

— Peak age 3–10 years (90% under age 10); boys slightly more affected

— Incidence ~10–20/100,000 children per year; rare in adults but more severe when it occurs

— Seasonal clustering in fall and winter, often following URI (group A strep, parvovirus B19, mycoplasma) or, less commonly, vaccinations or drug exposure

— Palpable purpura (mandatory, predominantly lower extremities/buttocks, non-thrombocytopenic)

— Abdominal pain (colicky, ~60–75%)

— Arthritis/arthralgia (~75%, large joints, lower extremity)

— Renal involvement (hematuria/proteinuria, 20–55%) OR biopsy showing IgA deposition

— Healthy child 4–8 years old with new palpable purpura on legs/buttocks, normal platelets, recent URI

— Child with periumbilical/colicky abdominal pain plus rash — think HSP before surgical abdomen

— Adolescent or adult with purpura, arthralgias, and microscopic hematuria

IgA vasculitis (Henoch-Schönlein purpura, HSP) is the most common systemic vasculitis of childhood, a small-vessel leukocytoclastic vasculitis driven by IgA1-containing immune complex deposition in skin, gut, joints, and glomeruli.

Epidemiology:

Pathogenesis pearl: Galactose-deficient IgA1 forms immune complexes → mesangial and dermal capillary deposition → complement activation and neutrophilic infiltration. Same biology as IgA nephropathy (Berger disease), which sits on the renal end of the same spectrum.

Classic tetrad (EULAR/PRINTO/PRES 2010 criteria require palpable purpura PLUS ≥1 of):

When to suspect on Step 3:

Board pearl: Palpable purpura with normal platelet count and normal coagulation studies in a school-aged child after a viral illness = IgA vasculitis until proven otherwise. Thrombocytopenia essentially rules HSP out and pushes you toward ITP, HUS, leukemia, or meningococcemia.

Step 3 management: Most cases are self-limited (4–6 weeks) and managed outpatient with supportive care, hydration, and scheduled urinalysis and BP monitoring to catch nephritis.

Presentation Patterns and Key History

— 1–3 weeks post-URI → arthralgias and abdominal pain often precede or coincide with rash

— Rash erupts in crops, starting as urticarial or erythematous macules → evolving into palpable purpura and ecchymoses over days

— Rash distribution is dependent and pressure-dependent: buttocks, posterior thighs, extensor legs; ankles and feet in ambulatory kids, back/scalp in infants

— Non-pruritic, non-blanching, symmetric

— May include bullae, necrosis, or scrotal/penile edema and pain (mimics testicular torsion — get Doppler if any doubt)

— Colicky periumbilical pain, often worse after meals; nausea, vomiting, occult or frank GI bleeding (hematochezia, melena)

— Intussusception (usually ileoileal, not ileocolic) in 3–4% — abdominal pain out of proportion, currant-jelly stools, palpable mass

— Pain may precede the rash by up to 2 weeks, creating a diagnostic trap

— Transient, migratory, non-destructive oligoarthritis of ankles and knees

— Periarticular swelling more than effusion; resolves without sequelae

— Onset usually within 4–6 weeks of presentation but can be delayed up to 6 months

— Hematuria (micro or gross), proteinuria, hypertension, rarely nephrotic/nephritic syndrome

— Recent infections, new medications (antibiotics, NSAIDs), vaccinations

— Family history of IgA nephropathy or autoimmunity

— Urine color changes, edema, decreased urine output

— Stool color, abdominal pain pattern

Typical sequence (helpful for stems):

Cutaneous history clues:

Gastrointestinal:

Joint:

Renal:

Key historical elements to ask:

Key distinction: In adults, HSP more often presents with severe renal disease and constitutional symptoms; in children, joint and GI complaints dominate and renal disease is usually mild.

Board pearl: A child with abdominal pain before the rash appears is the classic "missed HSP" stem — keep it on the differential for unexplained colicky pain in school-aged children.

Physical Exam Findings and Severity Assessment

— Usually well-appearing and afebrile or low-grade fever

— Check BP at every visit — new hypertension signals nephritis

— Tachycardia, orthostasis, or pallor → suspect significant GI bleeding or intussusception

— Palpable purpura — raised, non-blanching, 2–10 mm lesions; symmetric on buttocks and lower extremities

— Lesions in various stages (red papules → purpura → brown macules)

— In infants/toddlers: prominent edema of face, scalp, hands, feet, scrotum ("acute hemorrhagic edema of infancy" overlaps clinically)

— Look for bullae or skin necrosis (more common in adults; suggests severe vasculitis)

— Periarticular swelling and tenderness around ankles, knees, wrists

— Limp or refusal to walk in young children

— Joint motion preserved; no warmth or erythema typical of septic joint

— Diffuse tenderness, hyperactive bowel sounds, occult blood on rectal exam

— Sausage-shaped RUQ/periumbilical mass → intussusception

— Peritoneal signs → perforation, ischemia, surgical emergency

— Scrotal swelling, erythema, tenderness — HSP orchitis mimics torsion

— Doppler ultrasound is mandatory if torsion cannot be excluded clinically

— Headache, seizures, altered mental status from CNS vasculitis or PRES (severe HTN)

Vital signs / hemodynamics:

Skin (the diagnostic anchor):

Musculoskeletal:

Abdominal exam:

Genitourinary:

Neuro (rare but tested):

Step 3 management: At every HSP visit, document BP, urinalysis dipstick, abdominal exam, and skin distribution — these are the four parameters that decide outpatient vs. inpatient care and that drive long-term renal follow-up.

Board pearl: A child with HSP and acute scrotal pain must get a Doppler US; HSP-related scrotal vasculitis and testicular torsion can coexist clinically, and missing torsion is a malpractice trap.

Diagnostic Workup — Initial Labs, Urinalysis, and Imaging

— CBC with differential — platelets normal or elevated (rules out ITP, HUS, leukemia, meningococcemia)

— PT/PTT — normal (rules out coagulopathy)

— BMP — creatinine, BUN, electrolytes for renal function

— Urinalysis with microscopy — the single most important test for prognosis

· Hematuria (micro or gross), proteinuria, RBC casts

— Spot urine protein:creatinine ratio if dipstick positive (>0.2 abnormal in children >2 yr)

— Albumin — low if nephrotic-range proteinuria

— CRP/ESR — mildly elevated, nonspecific

— Serum IgA elevated in ~50% (not diagnostic, not needed routinely)

— C3/C4 normal (helps distinguish from lupus, post-strep GN, MPGN, cryoglobulinemia)

— ANA, ANCA negative — order if atypical features or adult patient

— ASO/anti-DNase B if recent pharyngitis suspected

— Stool guaiac/FIT for occult GI bleeding (often positive even without visible blood)

— Abdominal ultrasound for severe abdominal pain or suspected intussusception

· HSP intussusception is usually ileoileal → US > air enema (which only reaches ileocolic)

— Scrotal Doppler US for scrotal involvement to exclude torsion

— CT abdomen only if perforation, ischemia, or surgical abdomen suspected

HSP is a clinical diagnosis in the classic child — labs are obtained to rule out mimics and to assess organ involvement, not to confirm.

First-line labs in every suspected case:

Supporting but not required:

Stool studies:

Imaging — selective, not routine:

Key distinction: Platelet count is the pivotal first lab — normal/high platelets with palpable purpura = HSP/vasculitis; low platelets = ITP, HUS, TTP, leukemia, DIC, meningococcemia. This single number redirects the entire workup.

CCS pearl: Order CBC, BMP, UA, PT/PTT, stool guaiac, and BP on initial HSP encounter; reflex to abdominal US if pain is severe and to renal consult if proteinuria >0.5–1 g/day or rising creatinine.

Diagnostic Workup — Biopsy and Confirmatory Studies

— Atypical presentation: adult patient, absent purpura, prolonged course, severe renal disease

— Diagnosis unclear after clinical and lab evaluation

— Renal disease that is severe, persistent, or progressive — to guide immunosuppression

— Sample a fresh purpuric lesion (<24–48 hr old) for highest yield

— Light microscopy: leukocytoclastic vasculitis of postcapillary venules — neutrophilic infiltrate, nuclear debris, fibrinoid necrosis, RBC extravasation

— Direct immunofluorescence (DIF): IgA deposits in vessel walls — pathognomonic and distinguishes from other small-vessel vasculitides

— Also commonly shows C3, fibrin; IgM/IgG variable

— Indications (think Step 3 escalation triggers):

· Nephrotic-range proteinuria (>40 mg/m²/hr or UPCR >2)

· Persistent proteinuria >1 g/day beyond 4 weeks

· Impaired or declining GFR

· Hypertension with abnormal urinalysis

· Rapidly progressive glomerulonephritis (RPGN) picture

— Histology mirrors IgA nephropathy:

· Light microscopy: mesangial proliferation, ranging from focal to diffuse; crescents in severe cases

· Immunofluorescence: mesangial IgA deposits (also C3, IgG, IgM)

· EM: mesangial electron-dense deposits

— ISKDC classification (I–VI) by % crescents — guides prognosis and immunosuppression intensity

— Mandatory: palpable purpura (with lower limb predominance, not thrombocytopenic)

— Plus ≥1 of: diffuse abdominal pain, arthritis/arthralgia, renal involvement, or biopsy with predominant IgA deposition

When biopsy is indicated:

Skin biopsy:

Renal biopsy — the high-stakes decision:

EULAR/PRINTO/PRES 2010 classification criteria:

Board pearl: IgA on direct immunofluorescence in either skin or kidney is the histologic signature. In adults with palpable purpura, biopsy is almost always done because mimics (cryoglobulinemia, ANCA vasculitis, drug-induced LCV) are far more common.

Step 3 management: A child with persistent proteinuria >1 g/day, rising creatinine, or nephrotic syndrome should be referred to pediatric nephrology for renal biopsy to guide steroid/immunosuppressive therapy.

Risk Stratification and First-Line Management Logic

— Mild abdominal pain tolerating PO

— Normal renal function and BP

— No GI bleeding beyond trace guaiac positivity

— Reliable follow-up available

— Severe abdominal pain, persistent vomiting, or inability to maintain hydration

— Significant GI bleeding (hematochezia, melena, drop in Hb)

— Suspected intussusception, perforation, or ischemia

— Acute renal insufficiency, nephrotic syndrome, or RPGN

— Severe hypertension

— Neurologic symptoms (seizure, AMS)

— Scrotal involvement requiring observation

— Severe arthritis preventing ambulation

— No urinary findings or isolated microscopic hematuria → excellent prognosis, monitor only

— Hematuria + mild proteinuria → close follow-up, no immunosuppression

— Nephritic or nephrotic syndrome, or rising creatinine → biopsy + immunosuppression

— Hydration (PO or IV)

— Pain control: acetaminophen first-line; NSAIDs are relatively contraindicated if renal involvement or active GI bleeding, but can be used cautiously for arthritis when renal function and GI status are normal

— Rest, leg elevation for edema

— Skin care; avoid trauma

— Do NOT prevent renal disease (multiple RCTs/meta-analyses)

— Do reduce duration and severity of abdominal pain and arthritis and may reduce intussusception risk

— Reserved for moderate-severe GI involvement, severe arthritis, scrotal pain, or established nephritis

Triage decision at first encounter: Most children with uncomplicated HSP can be managed as outpatients; admission is reserved for specific red flags.

Outpatient candidates:

Admission criteria (Step 3 must-know):

Severity stratification by renal phenotype (predicts long-term outcome):

Supportive care backbone (applies to all):

Role of corticosteroids — nuanced:

Key distinction: Steroids in HSP are for symptom control and severe organ involvement, not for prophylaxis against nephritis. Routine steroid use in mild HSP is not indicated and is a common Step 3 distractor.

CCS pearl: First orders for mild HSP — outpatient follow-up, acetaminophen PRN, hydration, BP and UA at 1, 2, 4, 8, 12 weeks then monthly to 6 months, return precautions for severe abdominal pain or dark urine.

Pharmacotherapy — First-Line Regimens

— Acetaminophen 10–15 mg/kg q4–6h PRN for pain

— NSAIDs (ibuprofen 10 mg/kg q6–8h) for arthritis if renal function and GI exam normal

— No steroids, no antibiotics unless treating a documented infection

— Prednisone/prednisolone 1–2 mg/kg/day PO (max 60 mg) for 1–2 weeks, then taper over 2–4 weeks

— IV methylprednisolone if PO intake is poor or GI bleeding present

— Adjunct: PPI (omeprazole 1 mg/kg/day) for gastric protection during steroids/NSAIDs

— Stress-dose taper instructions; do not stop abruptly

— Isolated nephritic syndrome with mild proteinuria: ACE inhibitor (enalapril, lisinopril) for antiproteinuric effect; monitor K and creatinine

— Nephrotic-range proteinuria or crescentic GN:

· High-dose pulse methylprednisolone 30 mg/kg/day IV × 3 days (max 1 g) then oral prednisone

· Add steroid-sparing agent: cyclophosphamide, mycophenolate mofetil, azathioprine, or cyclosporine — choice driven by biopsy severity and pediatric nephrology

· Rituximab in refractory or relapsing cases

· Plasmapheresis considered in rapidly progressive GN with crescents on biopsy

— ACEi/ARB first-line for HSP nephritis-associated HTN and persistent proteinuria, even with normal BP

— Target BP <90th percentile for age/sex/height; <75th if proteinuria

— Only if a specific bacterial trigger is documented (e.g., GAS pharyngitis → penicillin)

— Empiric antibiotics are not standard

— Hold live vaccines during high-dose immunosuppression; resume per ACIP after immunosuppression weaned

— Inactivated vaccines (including annual flu) should continue

Mild disease (skin + mild arthritis only):

Moderate disease (severe abdominal pain, scrotal involvement, intractable arthritis):

Severe nephritis — escalation:

Antihypertensive therapy:

Antibiotics:

Vaccinations:

Board pearl: Steroids treat symptoms and severe organ disease, not the disease course. Prophylactic steroids in mild HSP do not prevent nephritis — a frequent wrong answer on boards.

Step 3 management: For any HSP child started on steroids, write orders for PPI, calcium/vitamin D, glucose monitoring, BP, and a clear taper schedule before discharge; include written return precautions.

Procedures and Expanded Pharmacology — Refractory and Complication Management

— Abdominal ultrasound for intussusception screening

— Air or saline enema reduction for ileocolic intussusception only; ileoileal usually requires surgical reduction

— Surgical exploration for perforation, infarction, or failed enema reduction

— Renal biopsy (percutaneous, US-guided) — pediatric nephrology procedure

— Plasmapheresis for severe crescentic GN or pulmonary-renal syndrome (rare)

— Cyclophosphamide: oral 2 mg/kg/day or IV pulses 500–750 mg/m² monthly; used for crescentic nephritis or severe systemic vasculitis

· Toxicity: hemorrhagic cystitis (give mesna and hydration), gonadal failure, secondary malignancy, marrow suppression

— Mycophenolate mofetil (MMF): 600 mg/m² BID; favored in pediatrics for steroid-sparing maintenance

· Toxicity: GI upset, leukopenia; check CBC

— Azathioprine: 1–2 mg/kg/day; check TPMT activity before initiation

— Cyclosporine/tacrolimus: useful for steroid-resistant nephrotic syndrome

· Monitor levels, BP, creatinine, glucose

— Rituximab: 375 mg/m² weekly × 4 or 750 mg/m² × 2; B-cell depletion for refractory cases

· Pre-medicate, screen for HBV

— IVIG: limited role, sometimes used in severe GI disease or relapse

— ACEi/ARB even when normotensive if persistent proteinuria

— Statin if persistent dyslipidemia from nephrotic syndrome

— Salt restriction; cautious diuresis for edema

— Pack RBC transfusion if Hb <7 or symptomatic GI bleed

— Albumin + furosemide for symptomatic anasarca in nephrotic phase

Procedures relevant to HSP are mostly diagnostic or for complications:

Refractory or severe disease pharmacology:

Adjuncts for nephritis maintenance:

Transfusion and supportive measures:

Board pearl: Plasmapheresis + pulse methylprednisolone + cyclophosphamide is the classic regimen for crescentic HSP nephritis (RPGN picture) — a high-yield scenario for atypical adult-onset cases.

CCS pearl: When ordering cyclophosphamide on the CCS interface, simultaneously order mesna, IV hydration, antiemetic, CBC with differential, and urinalysis; missing mesna is a graded omission.

Special Populations — Adults and Renal/Hepatic Impairment

— More likely to present with severe nephritis, GI involvement, and skin necrosis

— Higher rates of chronic kidney disease and ESRD (up to 30% long-term)

— Lower rates of spontaneous remission

— Renal biopsy almost always indicated; threshold for immunosuppression lower

— Workup must rigorously exclude malignancy (especially solid tumors, hematologic) and infection (HCV cryoglobulinemia, HIV, endocarditis) that can drive secondary IgA-dominant vasculitis

— Avoid NSAIDs entirely

— Dose-adjust cyclophosphamide, MMF reduced or held with severe cytopenia

— ACEi/ARB: start low, monitor K and creatinine; hold for >30% creatinine rise or K >5.5

— Renal replacement therapy criteria standard (AEIOU): refractory acidosis, electrolyte derangements, intoxication overload, uremia

— Avoid iodinated contrast when possible; if needed, hydrate and use lowest dose

— Acetaminophen dose reduction (<2 g/day in cirrhosis)

— Azathioprine and MMF require careful monitoring

— Avoid hepatotoxic NSAIDs

— Higher infection risk on immunosuppression — give PJP prophylaxis (TMP-SMX) with prolonged high-dose steroids/cyclophosphamide

— Bone protection: calcium, vitamin D, consider bisphosphonate if prolonged steroids

— Vaccinate against pneumococcus and influenza before immunosuppression when feasible

Adult-onset IgA vasculitis is uncommon but board-relevant:

Renal impairment (acute or chronic):

Hepatic impairment:

Elderly considerations (rare in HSP but applicable when present):

Key distinction: Adult HSP is not benign — renal outcomes are substantially worse than in children, and clinicians should escalate to biopsy and immunosuppression sooner. Pediatric reassurance about self-limited disease does not transfer.

Step 3 management: In any adult with palpable purpura, work up secondary causes (HCV, HIV, paraproteinemia, malignancy, drugs) in parallel with initiating supportive care — do not anchor on "adult HSP" without ruling these out.

Special Populations — Pregnancy, Infants, and Recurrence Risks

— Women with prior HSP nephritis are at risk for hypertension, preeclampsia, proteinuria, and disease flare during pregnancy

— Preconception counseling: aim for stable disease, off teratogenic agents (cyclophosphamide, MMF) for ≥3 months prior

— Pregnancy-compatible agents: azathioprine, hydroxychloroquine, low-dose prednisone, tacrolimus

— ACEi/ARB contraindicated in pregnancy — switch to labetalol, nifedipine, methyldopa for BP control

— Co-manage with MFM and nephrology; baseline UPCR, creatinine, BP early in pregnancy

— May present with acute hemorrhagic edema of infancy (AHEI) — a related but distinct entity with prominent face, ear, and extremity edema, large cockade-shaped purpura, and less systemic involvement

— AHEI is typically benign and self-limited within 1–3 weeks

— Renal involvement uncommon but still warrants UA screening

— Recurs in about one-third of children, usually within 4–6 months, milder than the initial episode

— Recurrence does not automatically mean nephritis; reassess organ involvement each time

— Persistent or recurrent disease in older children should prompt re-evaluation for IgA nephropathy or secondary causes

— Children may return to school once systemic symptoms resolve and skin lesions are not actively bleeding

— Avoid contact sports during active arthritis; resume gradually

— Immunization schedule continues per ACIP unless on high-dose immunosuppression

— Reassure that HSP is not contagious, not inherited, and usually self-limited

— Explain why long-term urine and BP monitoring is critical even after the rash fades

— Provide written return precautions: severe abdominal pain, vomiting, dark urine, decreased urine output, swelling, severe headache

Pregnancy and HSP:

Infants and toddlers (<2 years):

Pediatric recurrence:

School/sports:

Family counseling:

Board pearl: Acute hemorrhagic edema of infancy = HSP variant in kids <2 with dramatic skin findings but minimal systemic disease and excellent prognosis — recognize and reassure.

Step 3 management: Document recurrence in problem list and restart the urine/BP surveillance clock with each new flare.

Complications and Adverse Outcomes

— Intussusception (3–4%) — usually ileoileal; ultrasound is best initial study because enema only reaches ileocolic

— GI hemorrhage — occult to massive; transfusion may be needed

— Bowel perforation, ischemia, infarction — surgical emergencies

— Pancreatitis, protein-losing enteropathy, hydrops of gallbladder — rare

— HSP nephritis in 20–55% of children; severity ranges from isolated microscopic hematuria to crescentic GN

— Risk factors for chronic renal disease:

· Age >8 years at onset

· Persistent purpura >1 month

· Severe GI symptoms requiring steroids

· Nephrotic-range proteinuria at presentation

· Crescents on biopsy

— Long-term outcomes:

· Most pediatric cases recover fully

· ~1–7% progress to CKD or ESRD

· Adult HSP: ESRD risk up to 30%

— Late renal flares can occur years later — lifelong surveillance for those with biopsy-proven nephritis

— Orchitis/scrotal vasculitis (~10–20% of boys) — pain, swelling, must exclude torsion

— Ureteritis/ureteral stenosis — rare

— Transient arthritis, no permanent joint damage

— Functional limitation during acute phase

— Headache, seizure, encephalopathy, mononeuropathy

— Posterior reversible encephalopathy syndrome (PRES) from severe HTN

— Diffuse alveolar hemorrhage in severe systemic vasculitis

— Bullae, necrosis, secondary infection, post-inflammatory hyperpigmentation

— Steroid AEs: hyperglycemia, HTN, weight gain, mood, osteopenia, growth suppression

— Cyclophosphamide: cystitis, infertility, malignancy, infections

Gastrointestinal:

Renal — the dominant long-term concern:

Genitourinary:

Musculoskeletal:

Neurologic (rare):

Pulmonary (very rare but lethal):

Skin:

Treatment-related:

Key distinction: Recurrence ≠ chronic kidney disease. Most recurrences are mild skin/joint episodes; chronic renal disease is what determines long-term morbidity and dictates surveillance intensity.

Board pearl: Nephrotic-range proteinuria at presentation and crescents on biopsy are the two strongest predictors of progression to ESRD — these are the patients who need aggressive immunosuppression and lifelong nephrology follow-up.

When to Escalate Care — ICU, Consult, and Inpatient Triage

— Inability to tolerate PO / persistent vomiting

— Severe colicky abdominal pain not responding to acetaminophen

— GI bleeding (hematochezia, melena, hemodynamic change)

— Suspected intussusception, perforation, or surgical abdomen

— Acute scrotum (admit + urgent Doppler + surgical consult)

— New hypertension or BP at/above stage 2 thresholds

— Acute kidney injury or rapidly rising creatinine

— Nephrotic-range proteinuria, gross hematuria with hypertension, edema

— Neurologic symptoms: severe headache, seizure, AMS

— Severe systemic illness, fever, or concern for sepsis/meningococcemia

— Hemodynamic instability from GI bleed

— Diffuse alveolar hemorrhage (rare)

— Hypertensive emergency with end-organ injury / PRES

— Status epilepticus

— RPGN requiring urgent plasmapheresis and dialysis

— Pediatric nephrology: any significant proteinuria, AKI, persistent HTN, or biopsy candidacy

— Pediatric rheumatology: atypical presentation, refractory disease, or systemic vasculitis features

— Pediatric surgery: severe abdominal pain, suspected intussusception, perforation

— Pediatric urology: scrotal involvement when torsion cannot be excluded

— Dermatology: atypical rash or biopsy needs

— Hematology: if cytopenias appear or alternate diagnosis suspected

— Vital signs q4h with BP measurement

— Strict I/Os, daily weights

— Daily UA, BMP

— Stool guaiac × 3, monitor for occult blood

— Hemoglobin monitoring if GI bleed suspected

— Acetaminophen scheduled, steroids if indicated, PPI

— Pediatric nephrology consult if any renal abnormality

— Surgical consult on standby for abdominal red flags

— Tolerating PO and pain-controlled

— Stable Hb, no active GI bleeding

— Stable creatinine and BP

— Reliable outpatient follow-up arranged at 1 week

Pediatric ED triage red flags requiring admission:

ICU criteria:

Consultations to obtain:

CCS pearl on an inpatient HSP case, your standing orders should include:

Discharge readiness criteria:

Step 3 management: Don't miss surgical abdomen and torsion — these are the time-sensitive comorbid emergencies that overshadow the vasculitis itself. Always reassess abdomen and scrotum on every shift in admitted HSP patients.

Key Differentials — Same-Category (Vasculitic / Vasculopathic) Causes

— Granulomatosis with polyangiitis (GPA): upper + lower respiratory tract + renal, c-ANCA/PR3 positive, pauci-immune on biopsy

— Microscopic polyangiitis (MPA): pulmonary-renal syndrome, p-ANCA/MPO positive

— Eosinophilic granulomatosis with polyangiitis (EGPA): asthma, eosinophilia, neuropathy, p-ANCA in ~40%

— Key distinction: ANCA vasculitides show pauci-immune glomerulonephritis (no immune complexes) — opposite of HSP's IgA-rich deposits

— Adults, palpable purpura, arthralgia, neuropathy, glomerulonephritis

— Strong association with hepatitis C

— Low C4 (vs. normal in HSP), positive cryoglobulins, monoclonal gammopathy or RF positive

— Medium-vessel vasculitis; livedo, nodules, mononeuritis multiplex, mesenteric ischemia, hypertension

— No glomerulonephritis (renal artery aneurysms instead)

— Associated with HBV

— Children <5; fever >5 days, conjunctivitis, mucositis, rash (truncal, not purpuric), extremity changes, lymphadenopathy

— Coronary artery aneurysms are the feared complication

— Not purpuric — rash is polymorphous, blanching

— Recent drug exposure (penicillins, NSAIDs, sulfa, allopurinol)

— Predominantly cutaneous, leukocytoclastic, non-IgA on DIF

— Resolves with offending agent withdrawal

— Recurrent oral and genital ulcers, uveitis, pathergy; vasculitis of all vessel sizes

— Urticarial lesions lasting >24h, residual hyperpigmentation, often hypocomplementemic

— Normal → HSP, PAN, ANCA vasculitis

— Low → lupus, post-strep GN, MPGN, cryoglobulinemia, endocarditis

IgA vasculitis (HSP) — palpable purpura, normal platelets, IgA on DIF, lower extremity / buttock predominance, child <10 most often

ANCA-associated vasculitides:

Cryoglobulinemic vasculitis:

Polyarteritis nodosa (PAN):

Kawasaki disease:

Hypersensitivity vasculitis / drug-induced LCV:

Behçet disease:

Urticarial vasculitis:

Key distinction: C3/C4 is the cheap, fast triage lab:

Board pearl: Adult palpable purpura without an obvious cause demands ANCA, ANA, hepatitis B/C serologies, cryoglobulins, SPEP, and HIV before settling on "IgA vasculitis."

Key Differentials — Non-Vasculitic Mimics

— ITP: isolated thrombocytopenia, otherwise well child, post-viral

— TTP: pentad — MAHA, thrombocytopenia, neuro changes, renal dysfunction, fever; ADAMTS13 <10%

— HUS (typical, STEC): bloody diarrhea, MAHA, thrombocytopenia, AKI; schistocytes on smear

— DIC: critically ill, prolonged PT/PTT, low fibrinogen, elevated D-dimer

— Leukemia: pancytopenia, blasts, hepatosplenomegaly, bone pain

— Meningococcemia: rapidly progressive petechiae/purpura, fever, hypotension — empiric ceftriaxone immediately, do not wait for cultures

— Rocky Mountain spotted fever: fever, headache, rash starts on wrists/ankles spreading centripetally; doxycycline regardless of age

— Endocarditis: Janeway lesions, Osler nodes, splinter hemorrhages, fever, murmur, embolic phenomena

— Viral exanthems: parvovirus, EBV, CMV

— Bruises in non-dependent areas (trunk, ears, neck), patterned injuries, inconsistent history

— Always consider in young children with unexplained ecchymoses; mandatory reporting

— Hemophilia, von Willebrand disease — abnormal PT/PTT/PFA; bleeding history

— Vitamin K deficiency — neonates without prophylaxis

— Acute appendicitis, mesenteric adenitis, gastroenteritis, intussusception from other lead points

— Post-streptococcal GN: hematuria, edema, HTN, low C3, recent strep pharyngitis or impetigo

— IgA nephropathy (Berger disease): identical renal histology, but without systemic vasculitis — gross hematuria 1–3 days synpharyngitic

— Septic arthritis (mono-articular, fever, immobile joint)

— Transient synovitis (hip, post-viral)

— JIA (chronic, additive, may have systemic features)

Thrombocytopenia-driven purpura (platelets are LOW — opposite of HSP):

Infections that mimic vasculitis:

Non-accidental trauma:

Bleeding disorders:

Other GI/renal mimics:

Joint mimics:

Key distinction: HSP vs. HUS — both follow infections and have rash + GI symptoms, but HUS has thrombocytopenia, MAHA, schistocytes, and AKI as the dominant triad; HSP has normal platelets and palpable purpura.

Board pearl: Petechiae + fever + ill-appearing child = meningococcemia until proven otherwise — give ceftriaxone immediately, do not anchor on HSP.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Acetaminophen scheduled or PRN — pain control

— NSAIDs only if renal function normal and no GI bleeding

— Prednisone taper with explicit schedule and stop date if started inpatient

— PPI during steroid course

— ACEi/ARB for proteinuria or HTN — counsel on cough/hyperkalemia and avoidance during illness/dehydration

— Calcium and vitamin D if on prolonged steroids

— PJP prophylaxis (TMP-SMX 3 days/week) for patients on combined high-dose steroids + cyclophosphamide/rituximab

— Immunosuppression-specific monitoring labs (CBC, LFTs, drug levels)

— Update inactivated vaccines including annual influenza and COVID-19 per ACIP

— Defer live vaccines (MMR, varicella, LAIV, rotavirus, oral typhoid, yellow fever) during high-dose immunosuppression and for 1–3 months after

— Pneumococcal (PCV + PPSV23) and meningococcal if asplenia or persistent immunosuppression

— Adequate hydration

— Low-sodium diet if HTN or proteinuria

— Maintain physical activity once acute disease resolves

— Avoid known triggers (e.g., specific drugs that precipitated disease)

— Urinalysis and BP at 1, 2, 4, 8, 12 weeks post-onset, then monthly through 6 months

— Patients with normal UA at 6 months have very low risk of late renal disease and can be discharged from intensive surveillance

— Patients with persistent abnormalities → continue follow-up with nephrology

— Annual BP and UA for life in those with biopsy-proven nephritis

— Recurs in ~1/3 of children, usually within 4–6 months

— Each recurrence restarts the surveillance clock

— Pediatric to adult nephrology transition for adolescents with persistent nephritis

— Ensure problem list, biopsy results, and surveillance schedule travel with the patient

Discharge medication checklist:

Vaccination plan:

Lifestyle and dietary counseling:

Long-term surveillance plan (Step 3 high-yield):

Recurrence counseling:

Transition of care:

Board pearl: The single most important long-term action in HSP is serial urinalysis and BP measurement for 6 months — this is the action that prevents missed nephritis on the exam.

Step 3 management: Hand the family a written surveillance schedule at discharge — this counts as both quality of care and patient-safety best practice.

Follow-Up, Monitoring Parameters, and Counseling

— Week 1: clinic visit — BP, UA, dipstick, symptom review, medication adherence

— Weeks 2 and 4: BP + UA

— Months 2, 3, 6: BP + UA; consider UPCR if any dipstick abnormality

— Months 6–12: monthly to quarterly if any persistent findings

— Year 1 onward: annual BP + UA in those with prior nephritis

— BP plotted on age/sex/height nomogram

— Dipstick blood and protein; UPCR if dipstick positive

— Serum creatinine if proteinuria or elevated BP

— Albumin, lipid panel if nephrotic features

— Growth parameters (especially if on chronic steroids)

— Skin, joint, GI symptoms

— Worsening proteinuria, rising creatinine, or new nephrotic syndrome → repeat biopsy may be warranted

— Stable mild hematuria without proteinuria → continue observation, no repeat biopsy

— Disease is usually self-limited; rash and joint pain resolve within weeks

— Recurrences are common but usually milder

— Long-term concern is kidney involvement, which is why urine/BP checks matter

— Return immediately for: severe abdominal pain, vomiting blood or coffee-ground emesis, melena, hematochezia, decreased urination, dark/tea-colored urine, facial/leg swelling, severe headache, vision changes, scrotal pain

— Return to school when systemic symptoms resolve and patient is comfortable

— Activity modification during arthritis; avoid trauma to purpuric skin

— Document accommodations in writing if needed

— Address anxiety about chronic disease, especially in adolescents

— Adolescents transitioning to adult care need explicit education about self-management

— Reconcile medications at every visit

— Steroid tapers and ACEi titrations are frequent miscommunication points

Follow-up cadence (memorize for boards):

Parameters to track at each visit:

When to repeat labs / biopsy:

Counseling points for parents and patients:

School and activity:

Mental health:

Pharmacy and adherence:

Step 3 management: Schedule the first follow-up before discharge, give written instructions in plain language, and confirm the family has a thermometer, BP plan (or clinic access), and access to urine dipsticks if remote.

Board pearl: 6 months of normal UA and BP is the threshold at which the risk of new-onset HSP nephritis becomes negligible — a frequently tested follow-up duration.

Ethical, Legal, and Patient Safety Considerations

— Parental consent required for procedures (renal biopsy, surgery, invasive imaging)

— Pediatric assent for children ~7 years and older — explain in developmentally appropriate language

— For adolescents nearing the age of majority, involve them directly in treatment discussions, especially around fertility risks with cyclophosphamide

— Fertility preservation counseling (sperm banking, oocyte/ovarian tissue cryopreservation, GnRH agonists) should be offered before cyclophosphamide

— Bruising and purpura always require a non-accidental trauma assessment in young children before anchoring on a medical diagnosis

— Document distribution, history consistency, developmental plausibility

— File a child protective services report if abuse is suspected — mandated reporter responsibility regardless of certainty

— ED-to-floor and inpatient-to-outpatient handoffs are common failure points for HSP follow-up

— Closed-loop discharge: written follow-up appointment, surveillance schedule, return precautions, medication reconciliation, and direct communication with the PCP

— Adolescent-to-adult nephrology transition for those with chronic disease — start at age 14–16, complete by 18–21

— Surveillance UA/BP visits depend on insurance, transportation, and parental availability — identify barriers proactively and link to social work, community health workers, or home BP/urine programs

— Telehealth follow-up is appropriate for routine surveillance when in-person testing can be arranged

— Verify accurate weight-based dosing

— Provide written taper schedule (a top medication-error vector in pediatrics)

— Counsel on infection risk and immunization timing

— Steroid card / wallet card for patients on prolonged courses

— Avoid live vaccines during/after immunosuppression per ACIP timing

— Document immunization status before initiating biologics

— Confidential portions of the visit for adolescents (sexual health, substance use, mental health) per AAP/SAHM guidance

Informed consent and assent:

Mandatory reporting and child protection:

Transitions of care — high-risk Step 3 territory:

Health equity:

Safety in steroid prescribing:

Vaccination and immunosuppression coordination:

Privacy and adolescent care:

Board pearl: A young child with purpura in non-dependent, atypical locations (e.g., trunk, face, ears) deserves an explicit non-accidental trauma evaluation, not a reflexive HSP label — the legal and ethical stakes are high.

Step 3 management: Document the NAT consideration, mandated reporter status, and surveillance plan handoff in your discharge summary — these are graded items on management exams.

High-Yield Associations and Rapid-Fire Clinical Facts

Most common childhood vasculitis — pediatric Step 3 frequency favorite

Age 3–10, fall/winter, post-URI trigger (often group A strep)

Tetrad: palpable purpura, arthritis/arthralgia, abdominal pain, renal disease

Palpable purpura on buttocks and lower extremities with normal platelets — the diagnostic signature

EULAR/PRINTO/PRES criteria: palpable purpura mandatory + ≥1 of (abdominal pain, arthritis, renal involvement, IgA-predominant biopsy)

IgA1 immune complex deposition — same pathobiology as IgA nephropathy

Skin biopsy: leukocytoclastic vasculitis with IgA on DIF

Renal biopsy: mesangial IgA deposits, identical to IgA nephropathy

Normal C3/C4 — distinguishes from lupus, post-strep GN, MPGN, cryoglobulinemia

Intussusception is ileoileal (not ileocolic) — ultrasound > enema

Steroids do NOT prevent nephritis — they treat severe GI, joint, and renal disease

Pulse methylprednisolone + cyclophosphamide ± plasmapheresis for crescentic GN

ACEi/ARB for persistent proteinuria, even normotensive

Surveillance UA + BP for 6 months — gold standard follow-up

Recurrence ~33%, usually within 6 months, usually milder

Adult HSP: worse renal prognosis, must exclude HCV, malignancy, paraproteinemia

Acute hemorrhagic edema of infancy = benign HSP variant in <2-year-olds

Scrotal swelling: HSP orchitis vs. torsion → Doppler US mandatory

Thrombocytopenia rules out HSP — pivot to ITP, HUS, leukemia, meningococcemia

Stool guaiac positive even when no overt GI bleeding

Long-term ESRD risk: 1–7% in children, up to 30% in adults

Worst prognostic features: crescents, nephrotic-range proteinuria, age >8, persistent purpura >1 month, severe GI symptoms

NSAIDs OK for arthritis only if renal function and GI exam normal

Skin biopsy must be from a lesion <24–48 hours old for highest DIF yield

Cyclophosphamide: always co-order mesna and hydration; counsel on fertility

Live vaccines held during high-dose immunosuppression

Board pearl: When in doubt on a Step 3 stem, the single most discriminating finding for HSP is palpable purpura with normal platelet count in a 4–8-year-old after a viral illness.

Key distinction: HSP nephritis and IgA nephropathy are the same histologic disease in different clinical packages — both managed by nephrology with ACEi/ARB and immunosuppression as severity dictates.

Board Question Stem Patterns

— 6-year-old boy with rash on buttocks/legs, knee pain, periumbilical abdominal pain, recent URI. Platelets 320k. Best next step?

— Answer: Urinalysis (assess for renal involvement) — followed by supportive care and outpatient follow-up

— 7-year-old with 2 days of severe colicky abdominal pain; develops palpable purpura on legs the next day.

— Answer: HSP; obtain abdominal ultrasound to evaluate for ileoileal intussusception if pain is severe

— Child with purpura but platelets 15k → NOT HSP; think ITP (or leukemia if pancytopenic)

— Ill-appearing child with rapidly spreading petechiae/purpura and hypotension → meningococcemia; give ceftriaxone immediately

— 9-year-old HSP, 6 weeks later still has UPCR 2.5, BP 95th percentile. Best next step?

— Answer: Refer to pediatric nephrology for renal biopsy and start ACEi

— Mild HSP, parents ask if steroids will prevent kidney disease.

— Answer: No — steroids do not prevent nephritis; reserve for severe symptoms

— Boy with HSP develops acute scrotal pain and swelling.

— Answer: Scrotal Doppler ultrasound to rule out torsion before attributing to HSP

— 45-year-old with palpable purpura, arthralgia, hematuria, microscopic proteinuria.

— Answer: workup includes ANCA, ANA, HCV, HIV, cryoglobulins, SPEP/UPEP; biopsy likely required

— Family asks about prognosis. Recurs in ~1/3, usually within 4–6 months, usually milder; long-term prognosis depends on renal involvement

— How long to monitor UA/BP after HSP? 6 months with serial UA/BP

— Best initial imaging for suspected HSP intussusception? Ultrasound (because lesions are ileoileal, beyond enema reach)

— HSP patient with creatinine doubling and oliguria → biopsy shows crescents in 60% of glomeruli.

— Answer: Pulse methylprednisolone + cyclophosphamide ± plasmapheresis

Stem 1 — Classic pediatric presentation:

Stem 2 — The abdominal pain trap:

Stem 3 — The platelet pivot:

Stem 4 — The fever trap:

Stem 5 — Persistent proteinuria:

Stem 6 — Steroid question:

Stem 7 — Scrotal pain in HSP:

Stem 8 — Adult-onset purpura:

Stem 9 — Recurrence counseling:

Stem 10 — Follow-up cadence:

Stem 11 — Intussusception type:

Stem 12 — Rapidly progressive GN:

Board pearl: Boards reward you for ordering UA on every HSP patient and re-checking it serially — the most commonly missed correct answer in HSP stems is "urinalysis."

Step 3 management: When the stem asks "next best step," in HSP it is almost always a urinalysis, an ultrasound, or a referral to nephrology depending on what's missing in the scenario.

One-Line Recap

IgA vasculitis (Henoch-Schönlein purpura) is a small-vessel, IgA1 immune-complex vasculitis of school-aged children that presents with palpable purpura on the buttocks and lower extremities, abdominal pain, arthritis, and renal involvement — usually self-limited but defined long-term by the kidney, requiring 6 months of urinalysis and blood pressure surveillance.

— Diagnosis is clinical: palpable purpura (mandatory) + ≥1 of abdominal pain, arthritis, renal involvement, or IgA-predominant biopsy; normal platelets rule out the major mimics

— Workup at presentation: CBC, BMP, UA with microscopy, UPCR if dipstick positive, stool guaiac, BP — biopsy reserved for atypical, adult, or severe-renal cases

— Management is supportive: hydration, acetaminophen, judicious NSAIDs; steroids treat severe GI, joint, scrotal, or renal disease but do not prevent nephritis; ACEi/ARB for persistent proteinuria; pulse methylpred + cyclophosphamide ± plasmapheresis for crescentic GN

— Follow-up defines outcome: serial UA + BP at 1, 2, 4, 8, 12 weeks and 6 months; recurrence ~33%; long-term ESRD risk 1–7% in children, up to 30% in adults — refer to nephrology for any persistent proteinuria, hypertension, or renal dysfunction

— Intussusception (ileoileal — US, not enema) and bowel perforation in severe abdominal pain

— Scrotal pain — get a Doppler to exclude torsion

— Meningococcemia in any febrile, ill-appearing child with purpura — give empiric ceftriaxone

— Non-accidental trauma assessment for atypical purpura distribution in young children

High-yield recap bullets:

Don't-miss safety items:

Board pearl: If you remember only one thing — check the urinalysis and blood pressure on every visit for six months. That single behavior captures the natural history, prevents missed nephritis, and answers most Step 3 HSP follow-up questions.