[Case of Marfan syndrome with microscopic hematuria].

A 36-year-old man was admitted to our hospital for investigation of microscopic hematuria. He was very tall and presented arachnodactyly of the fingers and toes. Chest computed tomography and cardiac echography revealed annuloaortic ectasia and aortic regurgitation. Based on these findings, we suspected Marfan syndrome and performed gene analysis of the FBN1 gene, which encodes fibrillin-1. Mutational analysis showed the missence mutation, p. Ile 2585 Thr, present in exon 62 of the FBN1 gene. To investigate the genesis of microscopic and dismorphic hematuria, we performed a renal biopsy. Light microscopic analysis revealed the absence of any apparent histological changes in the glomerulus, small artery and arteriole. Electron microscopic analysis revealed the glomerular basement membrane to be irregularly thickened, however, there was neither any electron dense deposition nor fibrillar material. Marfan syndrome is an inherited disorder of connective tissue based on abnormality of the FBN1 gene. Fibfibrllin-1 acts not only as a component of microfibrils, but also as the regulator of transforming growth factor -beta signal transduction. From these points of view, we speculated that irregular formation of the glomerular basement membrane of our patient was induced by an imbalance in production of the extracellular matrix as the consequence of abnormal fibrillin-1--TGF-beta signaling.