Polymyositis with cardiac manifestations and unexpected immunology.

Polymyositis is an inflammatory myopathy of skeletal muscle. Cardiac involvement in the disease was first described in 1899 but has only been studied in detail over the past 20 years. About 10–15% of all patients with polymyositis have a cardiac abnormality as their initial presenting feature, while up to 70% of all those with polymyositis will have some cardiac involvement diagnosed non-invasively during the course of their illness. These can manifest either as cardiac failure; electrocardiographic changes, including nonspecific ST changes, and varying forms of AV block; myocarditis; valve disease and myocardial ischaemia in the presence of normal coronary vasculature. Myasthenia gravis is thought to be an autoimmune disease characterised by the presence of antibodies to the acetylcholine receptor of the motor end plate. Idiopathic forms are rarely associated with polymyositis, but a much stronger correlation exists in the presence of a thymoma, particularly in those with myocardial involvement, when anti-titin antibodies are usually present. However, thymoma is often less than 1 mm in size and therefore not visible on computed tomographic (CT) scanning. We describe a 56 year old woman with polymyositis, who initially presented with myocardial involvement and was also found to have antibodies consistent with myasthenia gravis.