Musculoskeletal Involvement in Dermatomyositis

The inflammatory myopathies are a heterogeneous group of chronic, subacute, or acute acquired diseases of skeletal muscle. Their common features are moderate to severe muscle weakness and inflammation in the skeletal muscles [1]. An analysis of 153 cases by Carl Pearson's group in 1977 forms the basis of current clinical knowledge of the musclar involvement in PM and DM [2].

Characteristically, DM patients develop progressive muscle weakness affecting the proximal muscles around the shoulders and hips (limb-girdle muscles), or neck muscles (ofthen in juvenile DM). The weakness is usually symmetric. In general, the onset is gradual and the disease develops relatively slowly, occurring over weeks to even months, and rarely appeares acute. In their series of 153 patients Bohan et al. (1977) reported that, on initial presentation, muscle strength was normal in 48 cases (31%) [2]. However, on occasions, the onset can be acute, with rapid development of weakness. The muscle involvement is the second most common presenting feature of DM, which varied between 53% and 96% of patients with skin rash [3–5] (Table 8.1). Almost all patients presented proximal muscle weakness in some studies [6, 7].