Cutaneous IgA vasculitis with crescentic nephropathy presenting with ulcers resembling pyoderma gangrenosum.

oedematous and yellowish wheals with peripheral erythema on her flanks and thighs for 48 h. She had no fever, and abdominal palpation was normal. A blood test showed hyperbilirubinaemia with total bilirubin 67 μmol/L and direct bilirubin 50 μmol/L. Lipase and haemoglobin levels were normal. A biliary echography showed choledochal lithiasis. Yellow urticaria was diagnosed. The patient received intravenous antihistamines, with rapid improvement. Yellow urticaria is an unusual urticaria variant that appears in patients with hyperbilirubinaemia. It differs from the usual type because of the yellow colour of the hives. This colour seems to be due to the diffusion of bilirubin to the interstitial extravascular sector of the dermis due to the increased capillary permeability induced by urticaria. The originality of our 2 cases show that the colour of the lesions should lead to suspect hyperbilirubinaemia. The origin of hyperbilirubinaemia can be hepatic, haemolytic or enzymatic defect. Most cases of yellow urticaria reported were associated with a liver failure with cholestasis. The triggering factor is not always found. In our first case, sepsis could be the cause. Some authors think that hyperbilirubinaemia or high serum bile acid levels may be responsible for triggering urticaria, through the direct activation of mast cells. The diagnosis of yellow urticaria is clinical and does not require a biopsy. Fleeting, migrating and oedematous plaques confirm urticaria. The distinctive feature of this urticaria is that the yellow lesions persist for several days similar to the yellow phase of a bruise. This is due to the affinity of bilirubin for elastin, which explains why the yellow colour persists even if bilirubinaemia returns to normal. The presence of yellow urticaria should suggest hyperbilirubinaemia and may allow the diagnosis of a previously undetected liver or biliary disease.