[A case of Alport syndrome diagnosed by immunofluorescence using a newly defined monoclonal antibody].

We report a case of Alport syndrome. The patient, a nine-year-old boy, showed macroscopic hematuria after an upper respiratory infection seven years ago. Microscopic hematuria with proteinuria was pointed out in routine urinalysis at school. He had no apparent familial history of either progressive renal diseases or deafness. Renal biopsy was performed at the age of eight, and he was diagnosed as focal segmental glomerulonephritis (mild) by light microscopy. Slight irregular thickening of the glomerular basement membrane (GBM) was observed focally by electron microscopy. Both light microscopy and electron microscopic examinations did not indicate a hereditary nephritis. The 28-kilodalton (kDa) monomers of the non-collagenous globular domain (NC-1) of type IV collagen were absent along renal glomerular capillary walls from the patient by indirect immunofluorescence while they were normally observed in glomerular capillary walls from healthy subjects and patients with a variety of non-hereditary glomerulonephritis. It was suggested that immunofluorescence using a monoclonal antibody for the NC-1 domain of type IV collagen is useful in the precise diagnosis of the patients with Alport syndrome.