Autosomal recessive MYPN mutations have been reported in only six families showing a mildly progressive nemaline or cap myopathy with cardiomyopathy in some patients.
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.