MYH9 and renal disease

MYH9 encodes one of three heavy chain isoforms for the non-muscle myosin II (NM II) molecule. NM II is involved in cell structure and shape and motility. Myosin II is very widely expressed but MYH9 is highly expressed in podocytes. MYH9 diseases are characterized by various combinations of autosomal dominant progressive, proteinuric renal disease, giant platelets with low platelet counts, progressive sensorineural hearing impairment, granulocyte inclusions, and in some patients also cataracts. Although the eponyms Epstein and Fechtner have been given to MYH9 renal syndromes, there is a spectrum of manifestations of MYH9 diseases that do not correlate perfectly with genotype. They are best described as MYH9-associated renal disease. The occurrence of progressive deafness and renal failure led to this condition being considered an Alport syndrome variant in the past, but phenotype as well as molecular genetics clearly separate the disorders.