The typical renal lesion is a focal, segmental proliferative glomerulonephritis. The disease begins with the sudden appearance of a purpuric skin rash that typically involves the extensor surfaces of the feet, legs, and arms and a strip across the buttocks. The purpuric lesions may start as small areas of urticaria that become indurated and palpable. Crops of new lesions may appear over days to several weeks. Most patients also have fever and polyarthralgia with associated periarticular tenderness and swelling of the ankles, knees, hips, wrists, and elbows.
Many patients develop edema of the hands and feet.
GI findings are common and include colicky abdominal pain, abdominal tenderness, and melena. Stool may test positive for occult blood. The disease usually remits after about 4 wk but often recurs at least once after a disease-free interval of several weeks. Diagnosis, Prognosis, and Treatment Diagnosis is based largely on recognition of clinical findings. Renal biopsy may help define the prognosis of the renal lesion.