nemaline myopathy type 4
nemaline myopathy type 4An autosomal dominant form (OMIM:609285) of nemaline myopathy, a family of disorders characterised by muscle weakness of varying severity and onset, and abnormal thread- or rod-like structures in muscle fibres on histologic examination.
NEM4 presents from infancy to childhood with hypotonia and proximal weakness, with minimal or no progression. Major motor milestones are delayed but independent ambulation is usually achieved; a wheelchair may be needed in later life.
Caused by defects of TPM2, which encodes beta-tropomyosin, an actin filament binding protein that binds to actin filaments in muscle and plays a central role in regulating striated muscle contraction.