Cause:Perhaps an IgA immune complex disease precipitated by URIs, strep throat, medications, or food allergies; but none of these is clearly associated
Pathophys:A small-vessel IgA immune complex vasculitis, with 4 systems involved: renal focal proliferative GN, skin purpura, joint arthritis, bowel edema and bleeding
Sx:H/o viral or bacterial infection 1-2 wk before (65%). Diffuse extensive purpura; abdominal pain, with nausea and vomiting often as 1st si, gi bleeding; hematuria; joint pain and swelling; fever
Si:Purpuric rash, palpable in 85%, esp over legs, arms, and buttocks; in adults, the rash blisters and ulcerates more, and more often involves the trunk; joint swelling
Usually benign and self-limited; <10% recurrence. In adults, morbidity and mortality may be higher, all from renal disease (Clin Nephrol 1989;311:60); others find outcomes similar in adults and children (Semin Arth Rheum 1991;21:103)
Bowel obstruction due to intussusception, may look like appendicitis; glomerular nephritis, nephrotic syndrome, and end-stage renal disease (5%)
r/o other small-vessel vasculitis (Vasculitis Etiologies)
Lab:
Chem:BUN and creatinine incr in 10-20%
Hem:Platelets normal
Path:Polys around, but usually not in small arteriole walls; this finding helps distinguish it from LEUKOCYTOCLASTIC VASCULITIS,which is seen in most systemic small-vessel vasculitis
Stool:Guaiac-positive
Urine:Hematuria and proteinuria in 50%
Rx:Steroids w azathioprine may help; antihistamines no help. Plasma exchange transfusions may help when rapidly progressive GN