IgA vasculitis (IgAV), formerly known as Henoch-Schönlein purpura (HSP), is a small-vessel vasculitis characterized by IgA immune complex deposition in blood vessels, affecting the skin, joints, gastrointestinal tract, and kidneys. It is closely related to IgA nephropathy (IgAN), sharing similar renal pathology, but IgAV involves systemic manifestations. Below is a concise overview of IgAV, covering its pathophysiology, clinical features, diagnosis, and management.

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Pathophysiology

• Mechanism:
  • Abnormal galactose-deficient IgA1 (Gd-IgA1) forms immune complexes that deposit in small vessel walls (arterioles, capillaries, venules).
  • This triggers inflammation, complement activation (C3), and tissue damage.
• Triggers:
  • Often follows mucosal infections (e.g., upper respiratory or gastrointestinal, especially Streptococcus).
  • Genetic predisposition and environmental factors may play a role.
• Affected Organs:
  • Skin: Purpuric rash due to dermal vessel inflammation.
  • Joints: Arthralgia from synovial inflammation.
  • GI tract: Vasculitis causing abdominal pain or bleeding.
  • Kidneys: Glomerulonephritis resembling IgA nephropathy.

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Clinical Features

• Classic Tetrad (not all present in every patient):
  1. Palpable Purpura:
     • Non-blanching, raised rash, typically on lower extremities and buttocks.
     • Mandatory for diagnosis; present in nearly 100% of cases.
  2. Arthralgia/Arthritis:
     • Pain and swelling in large joints (knees, ankles); transient and non-deforming.
     • Seen in ~60–80% of cases.
  3. Gastrointestinal Involvement:
     • Abdominal pain, nausea, vomiting, or GI bleeding (melena, hematochezia).
     • Rare: Intussusception (common in children), bowel perforation.
     • Occurs in ~50–75% of cases.
  4. Renal Involvement:
     • Hematuria (microscopic or macroscopic), proteinuria, or acute kidney injury (AKI).
     • Ranges from mild to severe glomerulonephritis (identical to IgA nephropathy).
     • Seen in ~20–50% of cases; more common in adults.
• Other Features:
  • Fever, fatigue, or scrotal pain/swelling (in males).
  • Rare: Neurological involvement (seizures, headache) or pulmonary hemorrhage.
• Epidemiology:
  • Most common vasculitis in children (peak age 4–10 years); rare in adults.
  • Males > females; higher incidence in fall/winter (post-infectious trigger).

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Diagnosis

1. Clinical Criteria (EULAR/PRINTO/PReS, 2010):
   • Mandatory: Palpable purpura (or petechiae) without thrombocytopenia.
   • Plus at least one of:
     • Diffuse abdominal pain.
     • Arthritis or arthralgia.
     • Renal involvement (hematuria or proteinuria).
     • Biopsy showing IgA-dominant immune deposits.
   • Diagnosis is clinical; biopsy reserved for atypical cases.
2. Laboratory Findings:
   • Urinalysis:
     • Hematuria (RBCs, dysmorphic RBCs indicating glomerular origin).
     • Proteinuria (mild to nephrotic-range in severe cases).
   • Serum Creatinine: Normal early; elevated in renal impairment.
   • Serum IgA: Elevated in ~50% of cases but not diagnostic.
   • Complement: Normal C3/C4 (unlike lupus or cryoglobulinemia).
   • CBC: Normal platelets (thrombocytopenia suggests other diagnoses, e.g., TTP).
   • Inflammatory Markers: Mildly elevated ESR/CRP in some cases.
   • Stool Testing: Guaiac-positive if GI bleeding.
3. Biopsy (if needed):
   • Skin: Leukocytoclastic vasculitis with IgA and C3 deposits in dermal vessels.
   • Kidney: Mesangial IgA deposits, identical to IgA nephropathy; crescents in severe cases.
   • Rarely performed unless diagnosis is uncertain or renal disease is severe.
4. Imaging (if GI symptoms):
   • Ultrasound or CT: Detect intussusception, bowel wall edema, or perforation.
5. Differential Diagnosis:
   • Other Vasculitides: ANCA-associated vasculitis, cryoglobulinemia (abnormal complement, hepatitis C).
   • Infections: Bacterial endocarditis, meningococcemia (thrombocytopenia, systemic signs).
   • Thrombotic Disorders: TTP, HUS (microangiopathic anemia, thrombocytopenia).
   • Lupus or Rheumatologic Diseases: Positive ANA, low complement.
   • Malignancy: Paraneoplastic vasculitis (rare).

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Management

1. Supportive Care (Most Cases):
   • Symptom Relief:
     • Analgesics (e.g., acetaminophen) or NSAIDs for joint pain (avoid NSAIDs if renal/GI involvement).
     • Hydration and rest for mild cases.
   • Monitoring:
     • Regular urinalysis, blood pressure, and renal function (creatinine, eGFR) for 6–12 months to detect renal involvement.
     • Most cases resolve spontaneously within weeks.
2. Renal Involvement:
   • Mild (hematuria, proteinuria <1 g/day):
     • Monitor closely; consider ACE inhibitors (ACEi) or Angiotensin Receptor Blockers (ARBs) for proteinuria or hypertension.
   • Moderate to Severe (proteinuria >1 g/day, AKI, crescents):
     • Corticosteroids: Prednisone (1 mg/kg/day, tapered) for significant renal disease or crescentic glomerulonephritis.
     • Immunosuppressants: Cyclophosphamide, mycophenolate mofetil, or rituximab for refractory or severe cases (evidence limited).
     • Emerging Therapies: Similar to IgA nephropathy (e.g., budesonide, SGLT2 inhibitors).
   • Dialysis: Rarely needed for severe AKI or progression to ESRD.
3. Gastrointestinal Involvement:
   • Mild: Supportive care (bowel rest, IV fluids).
   • Severe (GI bleeding, intussusception):
     • Corticosteroids (e.g., IV methylprednisolone).
     • Surgical consultation for intussusception or perforation.
4. Other Considerations:
   • Avoid Triggers: Treat underlying infections (e.g., streptococcal pharyngitis).
   • Vaccinations: Avoid live vaccines during immunosuppression.
   • Follow-Up: Long-term monitoring for renal disease (up to 20% develop chronic kidney disease, especially adults).

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Prognosis

• Children:
  • Most cases are self-limited, resolving within 4–6 weeks.
  • Renal involvement in ~20–50%; <5% progress to chronic kidney disease (CKD).
  • Recurrence in ~10–20% (often milder).
• Adults:
  • More likely to have severe renal involvement and progression to CKD or ESRD.
  • Worse prognosis with heavy proteinuria, hypertension, or crescents on biopsy.
• Long-Term:
  • Renal outcome drives prognosis; regular monitoring is critical, even after resolution of systemic symptoms.

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Key Points

• IgA Vasculitis: Small-vessel vasculitis with IgA immune complex deposition, affecting skin, joints, GI tract, and kidneys.
• Presentation: Palpable purpura (mandatory), arthralgia, abdominal pain, hematuria/proteinuria.
• Diagnosis: Clinical (purpura + one of abdominal pain, arthritis, renal involvement, or IgA deposits); biopsy rarely needed.
• Management: Supportive care for mild cases; corticosteroids for severe GI/renal involvement; ACEi/ARBs for proteinuria.
• Prognosis: Self-limited in most children; adults at higher risk for chronic renal disease.

Disclaimer: owerl is not a doctor; please consult one.