CASE 6 8 month-old male with hypotonia, failure to progress with motor milestones.

H&E stain
ATPase, pH 4.3 (type I fibers are brown)
ATPase, pH 10.4 (type II fibers are brown)

Diagnosis: Congenital myopathy with type I fiber predominance (Type II fiber hypoplasia) Although the presence of type I fiber predominance is nonspecific, when seen in neonates with congenital weakness it is thought to represent a distinct etiologic entity. The congenital myopathies, unlike the muscular dystrophies, tend to be indolent with good long-term prognoses. This page created on a Macintosh using PhotoPage by John A. Vink.