Nephronophthisis-like nephritis associated with fibrous dysplasia of bone

Nephronophthisis is a chronic tubulointerstitial nephritis with autosomal recessive inheritance whose evolution to end-stage renal disease is insidious but constant. Fibrous dysplasia of bone is characterized by focal replacement of normal bone and marrow with abnormal bone and fibrous tissue. We report on a young boy initially diagnosed with fibrous dysplasia of bone, who underwent renal investigation because of treatment with pamidronate. He presented with mild proteinuria (albuminuria/creatininuria 19 mg/mmol) and decreased glomerular filtration rate (GFR) (79 ml/min per 1.73 m(2) body surface area) leading to kidney biopsy, which showed nephronophthisis-like lesions, but neither NPHP1 gene deletion nor UMOD (uromodulin) mutation were identified. No association between fibrous dysplasia of bone and nephronophthisis has yet been described. Nephronophthisis-like nephritis associated with fibrous dysplasia of bone might represent a possible new syndrome in the nephronophthisis and medullary cystic kidney disease complex. However, a fortuitous association between these two conditions is also possible.