Heterozygous MYPN gene mutations are associated with hypertrophic, dilated, and restrictive cardiomyopathy, and homozygous loss-of-function truncating mutations have recently been identified in patients with cap myopathy, nemaline myopathy, and congenital myopathy with hanging big toe.
Autosomal recessive MYPN mutations have been reported in only six families showing a mildly progressive nemaline or cap myopathy with cardiomyopathy in some patients.