Renal infarction in a child with Henoch–Schönlein purpura

A 5-year-old boy with no relevant medical history presented with severe abdominal pain and purpura on the lower extremities, consistent with the diagnosis of Henoch–Schonlein purpura. Kidney function, blood pressure, and urinary parameters were normal. Repeated ultrasound investigations showed no evidence of intussusception and no renal abnormalities. The severity of the abdominal symptoms led to perform a digital subtraction angiography a week later, to rule out a vasculitis of medium- or large-sized arteries. No artery lesion was seen, but an infarction was present in the lower pole of the left kidney (Figure 1). At that moment, platelet count was decreasing (464 × 109/l at admission; 382 × 109/l on the day of angiography) and inflammatory parameters were high (C-reactive protein 93.9 mg/l; leukocytes 19.1 × 109/l). There was no evidence of volume depletion and no polycythemia. Blood pressure was normal. After 2 days, microhematuria was detected (>20 erythrocytes/high-power field). Genetic risk factors for thromboembolism, including protein C and protein S deficiency, activated protein C cell resistance and factor II mutation, were excluded. Lupus anticoagulant antibodies were negative. A diagnosis of Henoch–Schonlein purpura was established by immunoglobulin-A staining on skin biopsy, and was subsequently confirmed on renal biopsy, performed because of the onset of moderate transient proteinuria (1.48 g/l).