Scientists have strong evidence that the Coxsackie B virus plays a role in the onset of PM/DM. This was demonstrated by tracing antibodies in the serum and by tracing the virus in the muscle tissue. Other viruses are also suspect.
This type is very rare. About twenty cases have been reported after they had taken D-Penicillamine. When the treatment with this drug is discontinued, the symptoms disappear. Other cases after administration of cimetidine, penicillin, procainamide, hydralazine and propylthiouracil have been reported. Syndromes similar to PM/DM were seen after patients had taken drugs to lower the cholesterol level with statin.
PM/DM can occur as a part of other connective tissue diseases. Also other autoimmune diseases like Hashimoto thyroiditis (autoimmune inflammation of the thyroid gland) and pemphigus (autoimmune skin disease) may occur together with PM/DM.
Antinuclear antibodies are present in 67 % of the patients. Detailed tests sometimes show antibodies against a specific nucleus or cytoplasmatic (cytoplasm = part of the cell outside the nucleus, but inside the cell wall) antigens, namely PM1 (30 to 50% in PM, 5 to 10% in DM), Mi2 (5 to 10% in DM), Jo1 (10 to 30% in PM, especially with lung damage). These antibodies are a diagnostic aid but it does not imply that if they are not present, the diagnosis of the disease cannot be made.
In acute PM/DM with severe complaints, quick and intensive treatment is necessary with high to very high doses of IVIG , corticosteroids, TENS unit read the electronic section. The stage and severity of the disease determines the duration and the dose of the medication. Sometimes immunosuppressives have to be added to the corticosteroid treatment. Mostly azathioprine (Imuran) is used in fairly high doses (up to 3mg/kg-body weight each day).
The prognosis has improved considerably the past few years. The most important reason for this is an early diagnosis and treatment. If the first flare is suppressed, a permanent remission is seen in 60% of the cases after 2 to 5 years.