A progressive muscle disease affecting both sexes, with onset in first year of life, but cases of onset in adult life also reported. It is characterized by rodlike structures throughout the entire length of the muscle, formed by a core of tightly packed myofibrils in the centres of muscle fibres. The structures have a wormlike appearance, thus the synonym "nemalike myopathy." The pathologic fibrillar material is similar to and continuous with the substance that constitutes the Z-bands.
The affected infants have the appearance of floppy infants, with delayed physical development in walking - some patients take 5 years to start to walk - and subsequent develop nonprogressive muscle weakness. Normal mental development. Association with malignant hyperthermia syndrome reported in some families. The syndrome is probably transmitted as an autosomal dominant trait with variability in severity, but some authors suggest the existence of both dominant and recessive forms.
- G. M. Shy, K. R. Magee:
A new congenital nonprogresing myopathy.
Brain, Oxford, 1956, 79: 610-621.