MYH9 Mutation, the Hidden Face of Diverse Disease Spectrum - from Renal Perspective. Renal Perspective of MYH9 Mutation

MYH9 gene mutation results in a spectrum of diseases, such as May -Heglin anomaly and Epstein syndrome, depending upon the type of isoforms involved [1]. This mutation is inherited as an autosomal dominant entity and the gene encodes for non-muscle myosin heavy chain IIA (NMMHC-IIA) which is a part of myosin superfamily. The exact incidence of this disease in different populations is yet to be determined however, certain studies show the higher incidence in African-Americans [2,3]. Clinically, it presents frequently as macrothrombocytopenia, dohle inclusion bodies in polymorphs, sensorineural deafness, elevated liver enzymes, presenile cataract and renal involvement [4]. There is limited insight into the renal manifestations because of infrequent biopsy practice due to low platelet count. The majority of the patient suffering from nephritis present as proteinuria, haematuria or even progressive renal failure. Recent molecular studies revealed that there are many susceptibility loci in this gene associated with FSGS, HIV associated nephropathy (HIVAN) and non-diabetic end stage kidney disease. The pathogenesis of this entity is poorly understood however, it is considered that NMMHC-IIA protein is part of actin/myosin contractile apparatus located in the podocyte foot processes and its defect result in an abnormal filtration and defective podocyte matrix production.