PMC

Sequence alignment of MyHC IIa isoform among different species. Figure shows multiple sequence alignment of MyHC IIa across species in the amino acid region 1840–1900 of the human protein. The site of the L1870P mutation is indicated by an arrow. Invariant residues are grayed.

Muscle MRI. Axial T1-weighted fast spin echo sequences of pelvic girdle, thigh and calf muscles. At the pelvic level is an evident predominant involvement of gluteus maximus and tensor fascia lata (A). At the thigh vastus lateralis, rectus femoris, semitendinosus and gracilis are mainly involved (B). At calf level there are marked changes in the lateral head of the gastrocnemius and minor involvement of soleus (C).

Muscle biopsy. Quadriceps muscle biopsy shows marked variability in fiber size with proliferation of perimysial and endomysial connective tissue without inflammation and necrosis (A). Hystochemistry for cytocorme c-oxidase does not show disorganization of the intermyofibrillar network (B). Immunochemistry for Myosin isoforms shows type I fibers predominance (monoclonal antibodies against slow type I fibers, Leica Microsystems) (C). In (D) are shown the rare and hypotrophic type II fibers (monoclonal antibody against fast type fast IIa and IIx fibers, mAb A4.74, Hybridoma Bank, The University of Iowa, Department of Biology, Iowa City).