In both PM and DM, there may be involvement of organs other than muscle. In a surprising number of our cases of PM (and DM), cardiac abnormalities have been observed and in a small proportion of these, sudden death has occurred. The cardiac manifestations have taken the form of relatively minor electrocardiographic (ECG) changes, but several patients have had arrhythmias with clinical consequences. Among the fatal cases, about half have shown necrosis of myocardial fibers at autopsy, usually with only modest inflammatory changes. Interstitial lung disease is another known association in a few cases; its frequency ranges from 10 to 47 percent in different series and up to 70 percent in one subtype with anti-Jo antibodies (see further on under “Laboratory Diagnosis of PM and DM”), but the lower figure is probably correct. Exceptionally, there is a low-grade fever, especially if joint pain coexists.
Carcinoma with adult polymyositis or dermatomyositis
At one time this was a controversial subject and in some respects it remains so because of widely varying incidences of concurrence between systemic malignancy with PM and DM (see Engel et al and Buchbinder and Hill). In the large series reported by Sigurgeirsson and colleagues, 9 percent of 396 patients with PM were found to have carcinoma, either at the time of diagnosis of the muscle disease or within 5 years. DeVere and Bradley reported that 29 percent of their overall group of DM patients had an associated carcinoma; this figure rose to 40 percent if the patient was older than 40 years, and to 66 percent if the patient was both male and older than 40 years. This, however, is higher than reported in most other series. The relationship between myositis and malignancy is not understood; nonetheless, the connection appears valid, even if of uncertain frequency.
The neoplastic processes linked most often with myositis are lung and colon cancer in men and breast and ovarian cancer in women; however, tumors have been reported in nearly every organ of the body. In about half the cases, myositis antedates the clinical manifestations of the malignancy, sometimes by 1 to 2 years, an interval that has brought the association into question by several authors. The morbidity and mortality of patients with this combination is usually determined by the nature of the underlying tumor and its response to therapy. Occasionally, excision of the tumor is attended by remission of the myositis, but information on this point comes mostly from sporadic reports.
Dermatomyositis of Childhood
Idiopathic myositis occurs in children, but less frequently than in adults. Some cases tend to be relatively benign but otherwise do not differ from the syndrome in adults. More frequently, there is a distinctive illness, described by Banker and Victor, which differs in some respects from the usual adult form of the disease. In these children and adolescents, there is greater involvement of blood vessels in the connective tissue of multiple organs, as well as in skin and muscle. This childhood form of DM begins, as a rule, with typical skin changes accompanied by anorexia and fatigue. Erythematous discoloration of the upper eyelids (the previously noted heliotrope rash), frequently with facial edema, is another characteristic early sign. The erythema spreads to involve the periorbital regions, nose, malar areas, and upper lip as well as the skin over the knuckles, elbows, and knees. Cuticular overgrowth, subungual telangiectasia, and ulceration of the fingertips may be found. Capillary prominence in the nail beds and avascular regions in the cuticle are said to be characteristic but need to be sought with a magnifying lens or ophthalmoscope (these signs are also seen in the “CREST” [calcinosis cutis, Raynaud phenomenon, esophageal motility disorder, sclerodactyly, telangiectasia] form of scleroderma).