Definition:

Spheroid body myopathy (SBM) is a rare autosomal dominant neuromuscular disorder characterized by slowly progressing proximal muscle weakness and dysarthric nasal speech. The unique feature noted pathologically was the spheroid bodies found within the type I muscle fibers. SBM is caused by mutations in TTID/ MYOT. Myotilin induces actin filament bundling and stabilizes the assembled bundles.