Nephropathy of nail-patella syndrome.

Ultrastructural renal lesions of a sporadic case of nail-patella syndrome are described. Although the patient, an 8-year-old Japanese boy, had no clinical renal syndrome, electron microscopy disclosed the presence of collagen fibrils and electron lucent areas within glomerular basement membrane. Comparative observation of glomeruli in sections stained by uranyl-acetate and lead-citrate and those by PTAH-uranyl revealed evidence of many collagen fibrils in mesangial matrix, as well as glomerular basement membrane. At the follow-up study 3 years after the biopsy, he still showed normal urinalysis and no renal dysfunction. Characteristic ultrastructure of glomerulus of this disease can be present even in cases without any apparent clinical renal involvement. It is concluded that the glomerular lesions in nail-patella syndrome may be caused by abnormal metabolic processes of collagen in glomeruli rather than entrapment of circulating collagen precursors.