MYH7 and hydrops fetalis: Mutations in the MYH7 and MYBPC3 genes account for 40% of all HCM cases (62, 63), and individuals with double allele mutations in MYBPC3 develop a more HCM, in which the patient is predisposed to hypertrophy, severe systolic and diastolic dysfunction, progressive HF, and death within 1 year.