Alkaptonuria and renal failure: a case report and review of the literature.

In alkaptonuric ochronosis, the absence of homogentisic acid oxidase results in the accumulation of homogentisic acid in the body. Associated renal failure is rare and usually occurs in the later stages of the disease. We report a 19-yr-old girl who presented initially with severe renal failure, without family or past history of illness. There was no significant proteinuria or hematuria. No clinical evidence of pigmentation such as skin and subcutaneous cartilages was noted. However, pigment deposits were identified in the renal biopsy specimens obtained within a week after admission and another after a month. Two months later the peritoneal dialysis fluid and skin progressively darkened, suggesting ochronosis. This was confirmed by the detection of homogentisic acid in the serum and urine. The patient expired in renal failure. Renal biopsy tissues showed diffuse chronic tubulo-interstitial disease characterized by widespread tubular atrophy, interstitial fibrosis, and a moderate degree of inflammation. Many tubular cells contained brown, coarsely granular ochronotic pigment (OP) and a few pigment casts were in the lumina. Similar deposits were also in the interstitium and within histiocytes. Ultrastructural studies of the glomeruli revealed small sparse OP deposits in the visceral and parietal epithelial cells, mesangial cells, and rare extracellular and basement membrane deposits. The tubulointerstitial changes were varied: atrophy and dilatation of tubules, varying degrees of lysosomal OP and degeneration of tubular cells, casts containing OP with crystalline material, histiocytes distended with OP, and free interstitial pigment deposition.(ABSTRACT TRUNCATED AT 250 WORDS)