CKD in MYH9-Related Disorders

MYH9-related disorders are rare causes of chronic kidney disease (CKD) presenting as chronic glomerulonephritis and derive from mutations of the MYH9 gene, which encodes for the nonmuscle myosin heavy chain IIA. These disorders are autosomal dominant and include May-Hegglin anomaly and Sebastian, Fechtner, and Epstein syndromes. Diagnosis of these disorders is made first in early childhood because of the characteristic peripheral-blood smear findings of thrombocytopenia, giant platelets, and variably detected basophilic cytoplasmic inclusion bodies in leukocytes. CKD typically develops later in adulthood and may progress to end-stage renal disease. MYH9-related disorders may be associated with deafness and cataract; hence, Alport syndrome becomes important in the differential diagnosis. However, the autosomal dominance pattern of inheritance and characteristic peripheral-blood smear findings in the former help differentiate the two conditions. New evidence suggests that MYH9 gene alterations also are associated with a greater risk of focal segmental glomerulosclerosis and hypertensive nephrosclerosis in African Americans. The purpose of this review is to focus on the known, but rarely recognized association of MYH9-related disorders with CKD and highlight the recent discoveries related to the MYH9 gene that may explain the reason for a high CKD burden in African Americans.