An uncommon presentation of an uncommon nephropathy: the karyomegalic interstitial nephritis.

Karyomegalic interstitial nephritis (KIN) is a rare and certainly underdiagnosed nephropathy. It is characterized by a peculiar histological picture of interstitial nephritis associated with the presence of hyperchromatic, abnormally enlarged nuclei of tubular epithelial cells. KIN has an uncertain etiology, but should be suspected in young patients in the second or third decade of life presenting with progressive renal failure, proteinuria and/or hematuria and a history of recurrent respiratory infections. In these cases, the diagnosis should be suspected and confirmed by a renal biopsy. Herein, we report a case of KIN with atypical clinical presentation in a young patient with progressive kidney failure without proteinuria or hematuria or history of recurrent respiratory infections.