Muscle biopsy connective tissue

Figure 2. Erb s illustration of the pathology of muscle from patients with Duchenne muscular dystrophy. Note the variation in muscle fiber diameter, fiber-splitting, deposition of fat and infiltration of connective tissue. Drawing from several biopsies produced during final decade of 19th century. 

Muscle biopsy is usually undertaken to confirm the provisional clinical diagnosis. Because the skin lesions normally precede those in muscle, biopsies of muscle taken early may show little abnormality. Inflammatory foci may be scanty or absent and muscle fiber diameters may be normal. However typical biopsies show discrete foci of inflammatory cells, with a predominance of B-lymphocytes (see Figure 18). These cells are situated in perimysial connective tissue rather than in the en-domysium and are often also perivascular in location. Muscle fiber necrosis occurs in JDM but muscle fibers do not appear to be the primary target of the disordered immune process. Rather, it is the micro vasculature of the muscle which appears to degenerate first and muscle necrosis is preceded by capillary necrosis, detectable at the ultrastructural level. 

The neuromuscular complications of diabetes mellitus are most often neuropathic in origin, with distal sensorimotor polyneuropathies being the most common. In addition, ischemic infarction of skeletal muscle may occur due to occlusive vascular disease, with small and medium-sized arterioles particularly affected. This occurs in poorly-controlled diabetes and affects thigh, muscles in most cases. In acute stages, muscle biopsy findings are those of widespread muscle necrosis, edema, and phagocytic cell infiltration. Muscle regeneration may be incomplete and increased fibrous connective tissue may replace lost muscle tissue. 

Biopsies of gastrocnemius muscles in cases of poliomyelitis revealed that mucopolysaccharides were present in increased amount in the thickened connective tissue between atrophied muscle fibers (B12). Even though the vascular system of atrophic muscles was relatively unaffected, these sclerotic changes probably impair the nutrition of muscle fibers. 

Biopsy specimens (Kjellson 1953, Toussaint et al. 1959, Pecker et al. 1963, Harders andDiECKMANN 1964) and autopsy specimens (Reese and Bareta 1950, Cammermeyer 1956, Gordon and Hudson 1959, Edstrom et al.l959, Richterich et al. 1963, Alexander 1966) of the musculature show muscular atrophy as the predominant finding. Localized proliferation of connective tissue and small amounts of fat may be seen between muscle fiber bundles (Reese and Bareta 1950). 

Comment Alkaline phosphatase-positive proliferating endomysial connective tissue in muscle biopsies is unique to dermatomyositis, lupus, and some other collagen-vascular diseases. We think it is probably produced by proliferating disease-characteristic... 

---