Snapshot A 4-year-old boy presents to the emergency room with abdominal pain. His mother reports that he also had a rash for about a week on his lower extremities as well as joint pain and blood in his urine. Physical exam reveals palpable purpura on his buttocks and bilaterally on his legs and abdominal tenderness. On laboratory evaluation, there is no thrombocytopenia. The physician reassures his mother that this will resolve on its own and he will be monitored for renal involvement. Introduction Clinical definition also known as IgA vasculitis a systemic immune-mediated small vessel vasculitis often following an upper respiratory infection and characterized by IgA deposition and triad of palpable purpura arthralgias abdominal pain Epidemiology Demographics children < 10 years of age most common childhood vasculitis Risk factors fall and winter months family history upper respiratory tract infection especially with group A streptococcus or parvovirus B19 Etiology Associated with preceding upper respiratory infection Pathogenesis IgA immune complex deposition in the small vessels causes a vasculitis deposition in the skin, gastrointestinal tract, and renal glomeruli cause physical manifestations of the disease leukocytoclasis causes small vessel necrosis Associated conditions IgA nephropathy (Berger disease) Presentation Symptoms joint pains (arthralgias) of lower extremities colicky abdominal pain hematuria constitutional symptoms fever, malaise, or fatigue Physical exam symmetric palpable nontender purpura on buttocks and lower extremities typically the first sign of the disease may spread to upper extremities abdominal tenderness on palpation typically 1 week after onset of rash but can occur simultaneously Studies Labs normal platelet count presence of thrombocytopenia should prompt investigation into other causes of palpable purpura normal coagulation profile urine studies proteinuria and hematuria indicates renal involvement Biopsy indications most accurate test but usually not necessary only indicated if the diagnosis is uncertain findings IgA deposition in small vessels seen on direct immunofluorescence leukocytoclasis Differential Thrombotic thrombocytopenic purpura distinguishing factors FATRN Fever Anemia (microangiopathic hemolytic) Thrombocytopenia Renal failure Neurological symptoms schistocytes on peripheral blood smear Polyarteritis nodosa distinguishing factors usually in adults typically presents with ulcerative lesions but can also present with palpable purpura associated with hepatitis B virus infection "string of beads" (microaneurysms) on angiogram DIAGNOSIS Making the diagnosis most cases are clinically diagnosed Treatment Management approach as the disease resolves spontaneously over time, medical therapy is typically unnecessary, unless there is persistent nephropathy Conservative supportive care indication for all patients modalities hydration pain management Medical angiotensin-converting enzyme (ACE) inhibitor indication for patients with persistent proteinuria corticosteroids indications for patients with persistent proteinuria despite ACE-inhibitors not recommended for prevention of renal disease Complications Persistent renal sequelae Intussusception Recurrence Prognosis Resolves spontaneously over time Typically lasts 4 weeks