Incidence and type of pathologic alterations observed in muscle in a routine autopsy survey

MUSCLE BIOPSY is a common diagnostic procedure used in the work-up of persons with various forms of muscular or neuromuscular disease, as well as in a number of ill defined systemic disorders or in persons with fever of obscure origin. In the former groups, a reasonable approximation of the nature of the neurologic disease can be made in many of the cases, provided that the site for muscle biopsy is carefully selected. In the latter group, however, rarely does one discover a specific feature that would allow further clarification of the perplexing underlying disease process. If degenerative changes are observed in the muscle fibers or interstitial or perivascular inflammatory infiltrates are found, these are considered to be “consistent with the disease under consideration,” which is often one of the connective tissue or collagen disorders. It has not been generally appreciated that a number of similar or identical changes may occur in a wide variety of chronic disease states that are unrelated to the collagen diseases. Many years ago, Zenker23 pointed out that a characteristic hyalinizing change may affect the sarcoplasmic constituents of the muscle fibers in many cases of typhoid fever. This change has since been known as Zenker’s degeneration. Identical changes have been noted in a variety of infectious diseases, and the rectus abdominis has been the muscle most commonly affected, although a detailed survey of the body musculature has not been undertaken. These various diseases include epidemic influenza,22 pneumonia,’Ss small pox, paratyphoid fever, infectious hepatitis, Weil’s disease (leptospirosis), and others. In all of these conditions, the myopathy is thought to be caused by a circulating toxin liberated by the infectious agent. Organisms have not been found in the muscle lesions, with the single recent exception that Sheldon16 has demonstrated leptospiral antigen (presumably the organisms) in the vicinity of necrotic muscle lesions in Weil’s disease with the aid of the fluorescent-labeled antibody technic. Myositis, or inflammatory infiltrates in muscle, are always found in direct bacterial infections and most parasitic invasions of muscle. They are also present, but in variable degrees, in dermatomyositis and polymyositis.l3. 20 In recent years, it has been recognized that focal interstitial or perivascular collections of chronic inflammatory cells are commonly present in all of the collagen diseases, especially rheumatoid arthritis. ’ Furthermore, focal interstitial infiltrates of small lymphocytes, so-called lymphorrhages, are frequently seen in myasthenia gravis. As will be pointed out, focal myositis may occur in a variety of disease states other than the collagen diseases, but, in our material, it is not as common as degeneration. Most of the myopathic or neuromuscular disorders can only be strongly suspected by their histologic appearance, and there are only a few specific entities that can be diagnosed with certainty from the muscle biopsy. These include polyarteritis, sarcoidosis,”ln amyloidosis, tuberculosis, trichinosis, toxoplasmosis and certain other parasitic infestations, and metastatic malignancy. This survey of the histopathology of a series of muscles in routine autopsy material