Light chain nephropathy in a 19-month-old boy with AIDS.

A 19-month-old boy with AIDS developed clinically unexplainable proteinuria. Biopsied renal tissue was examined by light microscopy, transmission electron microscopy, and immunofluorescence. Findings included an increase of mesangial matrix with occasional nodular sclerosis, mesangial hypercellularity, and glomerular deposits of kappa and lambda light chains. There were deposits of kappa, but not lambda, light chains in the arteriolar walls, and around the tubular and interstitial capillary basement membranes. Quantitative urinary immunoelectrophoresis revealed an extremely high urinary concentration of kappa light chain. These changes are diagnostic of light chain nephropathy. The rarity of light chain nephropathy in childhood and its occurrence in a patient with AIDS make this case unusual.