Figure 2

Pathological findings in skeletal muscle from an affected puppy are suggestive of a diagnosis of XLMTM or other form of CNM. Cryosections of the biceps femoris muscle from the affected puppy III-2 were evaluated with a standard panel of histochemical stains and reactions. Marked variability in myofiber size was noted (A) with numerous hypotrophic fibers containing central nuclei. Most hypotrophic fibers were of type 1 as determined by staining with antibodies against slow (brown stain, type 1 fibers) and fast (pink stain, type 2 fibers) myosin heavy chains (B). Dense central and subsarcolemmal deposits were noted with the oxidative reactions SDH (C) and COX (D).