Trypsin digestion on paraffin sections is a useful tool for diagnosis of alport syndrome.

Trypsin digestion for 90 min revealed the alpha(5) chain of type IV collagen along the glomerular basement membrane and Bowman's capsule in paraffin-embedded renal sections of controls. In the 9 patients with the ultrastructures suggestive of Alport syndrome (AS), 8 patients were classified as X-linked dominant type due to the lack or mosaic pattern of alpha(5) chain in paraffin sections of renal biopsies by trypsin digestion, and 1 patient was classified as autosomal recessive type due to the lack of alpha(5) chain in the glomerular basement membrane only. Trypsin digestion is useful for the diagnosis of AS in paraffin-embedded renal tissue.