Tubular proteinuria in children without other defects of renal function

3 patients are described in whom proteinuria was detected on routine urine analysis and subsequently shown to be predominantly tubular in origin. Renal biopsies showed only minor changes. Hypercalciuria was also noted in 1 of the 3 patients but no other tubular abnormalities were demonstrated. The precise diagnosis remains uncertain, but an unusual presentation of idiopathic hypercalciuria or of the adult Fanconi syndrome must be considered. These patients may alternatively have a previously undescribed disorder.