Homozygous mutation in <i>MYH7</i> in myosin storage myopathy and cardiomyopathy

Abstract

Myosin storage myopathy (MSM) associated with mutations in MYH7 encoding for slow/β-cardiac myosin heavy chain (MyHC) occurs sporadically or shows autosomal dominant inheritance.1–4 MSM is usually associated with severe skeletal muscle weakness, but cardiomyopathy is typically not present. We describe a patient with MSM in whom there was a homozygous mutation (Glu1,883Lys) in MYH7 . The parents were second cousins, and three of their children developed progressive MSM with respiratory muscle weakness and hypertrophic cardiomyopathy. This British family consisted of four siblings, three of whom were affected; the parents were second cousins. There was no family history of muscle weakness. The father died with a stroke at age 58 and the mother with myocardial infarct at age 70. ### Case 1. Exertional dyspnea commenced in late adolescence for this patient. She presented at age 26 in heart failure, with elevated jugular venous pressure (8 cm), soft systolic murmur at the left sternal edge, and fourth heart sound. She was short (height 141 cm), with thoracic scoliosis. Lung function tests revealed a restrictive deficit. EKG showed right bundle branch block, right axis deviation, and sinus tachycardia. Echocardiography and cardiac catheterization revealed hypertrophic, nonobstructive cardiomyopathy with elevated right ventricular pressure (40 mm Hg systolic) and a restrictive right and left ventricular pattern. Five years later, she developed an acute supraventricular dysrthythmia. …