Muscle Lesions in Rheumatoid Arthritis.

Recently certain pathological investigations have indicated that there is frequently widespread involvement of the neuromuscular system in rheumatoid arthritis, and it has been suggested that this may be responsible for the prominent neuromuscular clinical features of the disease. Curtis and Pollard (1940) were the first to describe the non-articular lesion which was common to all their eleven cases of rheumatoid arthritis, inxcluding four cases with " Felty's Syndrome ". In every one of their eleven cases these authors found small perivascular infiltrations of lymphocytes in the muscles. Steiner and others (1946) performed muscle biopsies on seven cases of rheumatoid arthritis and demonstrated inflammatory nodules in each of the cases. The nodules were situated in the perimysium and in the endomysium, rarely in the epimysium. The nodules consisted of collections of lymphocytes and plasma cells and the authors termed the lesion " nodular polymyositis ". Similar lesions were encountered in the muscles of two cases which were examined at autopsy. The size of the nodules varied from very small ones (consisting of "twenty or less lymphocytes ") to large ones visible to the naked eye in the stained sections. They also noted definite arteritis and peri-arteritis in the small muscular vessels in some of their cases. In addition to the nodular inflammatory lesions they noted the occurrence of various stages of degeneration and atrophy of the muscle fibres and considered that these degenerative changes, when present, were always secondary to the inflammatory changes. The lesions were found in muscles which were not adjacent to affected joints, and were present even in long-standing cases of rheumatoid arthritis which were " seemingly burnt-out ". They suggested that these findings were specifictorheumatoid arthritis. These results were soon confirmed by other investigators. Gibson and others (1946) noted the presence of these nodular inflammatory lesions by biopsy in each of eleven cases of rheumatoid arthritis. De Forest and others (1947) found similar characteristic lesions in twelve out of sixteen muscle biopsies. Clawson and others (1947) demonstrated these characteristic lesions in seventeen out of forty-four deltoid muscle biopsies. Desmarais and others (1948) reported the results of muscle biopsies on a further fifty-six cases of typical idiopathic rheumatoid arthritis. Thirtyfour of these cases showed round-cell foci and bloodvessel changes. Like Steiner and others, they noted " positive " biopsies in cases which appeared " burnt-out ", in cases without muscle wasting, and in muscles remote from affected joints. Bunim and others (1948) stated that they found the..characteristic small nodules in the " large majority " of the muscle biopsies performed on twenty-five cases of typical rheumatoid arthritis. It thus appears, when these results are analysed, that " positive " muscle biopsies (with " nodular myositis ") occurred in 40 to 100 per cent. of cases of rheumatoid arthritis. If the results are totalled it appears that, on the average, approximately 60 per cent. of muscle biopsies in rheumatoid arthritis reveal the characteristic lesions described by Steiner and others (1946). Morrison and others (1947) examined the muscles of fourteen cases of rheumatoid arthritis at autopsy and encountered varying sizes of inflammatory nodules in eight instances.