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Source: Hill CL, et al. Frequency of specific cancer types in dermatomyositis and polymyositis: A population-based study. Lancet 2001;357:96-100.
Sigurgeirsson previously noted an increased association of cancer in adults who developed dermatomyositis and polymyositis (N Eng J Med 1992; 326:363-37). At that time, statistics were low, and specific associated cancers were not explicitly designated. This current report fills in those desired factors and provides the incidence of paraneoplastic dermatomyositis and polymyositis in patients in Sweden, Denmark, and Finland. Only patients who were in hospitals were included, reducing the overall potential association of ambulatory patients.
Based on hospital discharges from 1964-1983, 618 patients developed dermatomyositis and 914 had polymyositis. Mean age was approximately 55-57 years for cancer occurrence in each cohort. Lifetime cancer associated with dermatomyositis amounted to 198 total (32%) of which 115 developed within five years after the diagnosis of dermatomyositis. Polymyositis patients had 137 cancers, of which 95 developed after the polymyositis developed. With dermatomyositis the most frequent cancer risks consisted of ovary, lung, pancreas, stomach, colorectal cancers, and lymphomas. Polymyositis was followed by the identity of lung and bladder cancers as well as non-Hodgkins lymphoma. The risks of developing ovarian, pancreatic, and lung cancer lasted more than five years after patients who developed dermatomyositis. Within the cohort of patients suffering dermatomyositis, a number had already had a modest number of cancers within two years before the disease appeared. This especially applied to those age 45 years or older. No patients younger than 45 years of age with polymyositis had abnormal cancer rates. The risk increased after that age, mostly within two years or less before the polymyositis appeared. A similar closeness was linked to the emergence of dermatomyositis.
Dermatomyositis and polymyositis appearing in middle aged persons provide a major warning that antibodies from systemic malignancies or other perturbed immune molecules are on the paraneoplastic loose. Admittedly, many persons with these disorders may choose rheumatologists or dermatologists to cure their disorder. Nevertheless, neurologists with strong ties to peripheral neurology may be called upon because of the muscular pain, tenderness, and swelling that may develop. This clear clinical descriptive report indicates that dermatomyositis in patients older than 50 years has a 300% cancer risk above normal while polymyositis was associated with a 30% risk. The rates would be higher had the survey included the number of patients who had cancer during the year before the skin-muscle abnormality. The report is entirely descriptive and the several types of cancer involved make it difficult to even guess the origins of the circulating paraneoplastic antigen. Unfortunately, no mention is given to what happens following the treatment of the cancer. Were there any cures of either the cancers or the paraneoplastic molecules that together or independently developed the skin and muscle antibody reactions? Neurology Alert awaits a modern scientific answer to this now well known problem. —Fred Plum