TWO REPORTS appeared almost simultaneously, in 1963, describing a new myopathy. The condition was characterized pathologically by nuṃerous inclusions in muscle fibers referred to variously as myogranules, nemaline (thread-like) structures, or rod-like bodies.1,2 These initial cases together with other subsequent reports3-8 were considered to represent a disease entity with identical pathological findings and many of the following clinical features: "floppy infant"; delayed motor development; proximal limb weakness, usually with hypotonia; reduced muscle bulk; reflexes usually absent; onset from birth, most noticeable on initial attempt to walk; associated deformities, particularly pes cavus, high-arched palate, kyphosis or scoliosis; possibly (autosomal) dominant inheritance; and extremely slow or nonprogressive course. Since this disorder was first brought to light, Engel and Resnick9 and Engel10 described a disorder in which there were rodlike structures but this disorder was of late onset, noninherited, and progressive. The question has therefore been raised whether