FIGURE 2.

Skeletal muscle, heart, and sural nerve pathology. Dystrophic pathology was evident in H&E-stained cryosections from muscles evaluated as a diagnostic biopsy at age 1 year (A, quadriceps) or autopsy (B, quadriceps; C, biceps; D, diaphragm). Immunofluorescence studies performed in quadriceps obtained at autopsy showed normal expression of dystrophin (E) and α-dystroglycan (F, IIH6). In contrast, merosin was absent (G, 5H2 80 kDa antibody). Other isoforms of laminin were expressed in skeletal muscle basement membranes (H, polyclonal laminin antibody; I, laminin α5). Cardiac muscle evaluated at autopsy showed multifocal sites of lymphocytic aggregation, consistent with myocarditis (J, H&E). Immunofluorescence studies performed in the heart showed normal expression of dystrophin (K) but the total absence of merosin (L). Laminin α5 was strongly expressed (M). Abnormally thin myelin sheaths were noted by electron microscopy of the sural nerve (black arrow in N). The white arrow points to an axon with normal thickness myelin sheath. The scale bar in panel D is 100 µm for panels A–D and J–M; the scale bar in panel I is 100 µm for panels E–M. The scale bar in panel N is 2 µm. H&E, hematoxylin and eosin.