Acute plasmacytic interstitial nephritis in a child with Down syndrome

A 7.5-year-old boy with Down syndrome presented in acute renal failure (ARF) needing dialysis. When 1.5 years old he had a neuroblastoma, was treated for 1 year with chemotherapy and radiotherapy, and off chemotherapy had since been in remission. Renal biopsy revealed an interstitial inflammation, principally of plasma cells with some lymphocytes and eosinophils. Immunofluorescence showed no deposition of immunoglobulins or complement (C3). The plasma cells were a mixture of kappa and lambda light chain-producing cells. The patient spontaneously improved a week after admission. Initial ultrasonography showed enlarged kidneys with loss of corticomedullary differentiation. We are unaware of a report of ARF in a child, resulting primarily from a polyclonal plasmacytic interstitial nephritis. The etiology remains unclear.