A type of nemaline myopathy with characteristics of distal muscle weakness and sometimes slowness of muscle contraction. Onset is around 10 years of age, with initial presentation of symmetric weakness of ankle dorsiflexion and foot drop, or a general slowness of muscle contraction. All movements at the ankle and more proximal limb muscles may be disturbed. Weakness is slowly progressive. Facial, respiratory and cardiac muscles are generally normal, but patients are unable to jump or run because of muscle weakness or slowness. This form of nemaline myopathy is caused by mutations in the ACTA1 (1q42.13), NEB (2q22), TPM2 (9p13.3) or TPM3 (1q21.2) genes. Transmission follows an autosomal dominant pattern. [from
SNOMEDCT_US]