nemaline myopathy

a genetically and clinically heterogeneous, mainly congenital myopathy, characterized histologically by the presence of small, rodlike particles in the muscle fibers. Inheritance can be either autosomal dominant or autosomal recessive. The most common form presents as hypotonia and muscle weakness in infancy and is nonprogressive or slowly progressive. A more severe form is characterized by profound hypotonia and respiratory distress, arthrogryposis, and death in the first few months of life. A late-onset form, marked by mild proximal weakness beginning in early adulthood, has been reported, and rare sporadic cases are also seen.