Karyomegalic interstitial nephritis: a pitfall in urine cytology.

A case of a 44-yr-old Maori female presenting with chronic renal failure due to karyomegalic interstitial nephritis is reported. To our knowledge, this is the first instance this disorder has been reported in a New Zealand Maori. Karyomegalic interstitial nephritis is a rare cause of progressive renal failure, which may be familial, and is frequently associated with a history of recurrent respiratory infections. The urine in this case contained large, pleomorphic cells, mimicking carcinoma. The case therefore illustrates a rare cause of chronic renal failure, and presents an important diagnostic pitfall in the practice of urine cytopathology.