Adult Dermatomyositis

The incidence of these syndromes seems to vary according to geographical area and ethnic background but is about 0.2-0.3 per 100,000.population (mean annual incidence rate). However incidence rates calculated for adult populations are up to three times higher. The fifth and sixth decades show peak incidence rates and there is also clear biomodality across the full age spectrum due to the existence of a juvenile form of dermatomyositis (JDM) which is pathogenetically distinct. Polymyositis, uncomplicated by skin changes, can also occur as a juvenile condition. 

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

Inflammatory muscle diseases include dermatomyositis (DM) and polymyositis (PM) (Dalakas Hohlfeld, 2003). These diseases affect skeletal muscle and/or skin, leading to profound tissue modification. The prevalence of these diseases is approximately 5 cases per 100 000 (Jacobson et al., 1997). Dermatomyositis, affecting both children and adults, is more common than polymyositis, which strongly predominates in adults. Women are... 

The connective tissue diseases (CTDs) are a heterogeneous group of immuno-logically mediated inflammatory conditions of unknown etiology, accompanied by diverse autoantibodies and affecting multiple organ systems. In adults, the more frequent CTDs comprise rheumatoid arthritis (RA), systemic sclerosis (SSc), Sjogren s syndrome (SjS), systemic lupus erythematosus (SLE), polymyositis/ dermatomyositis (PM/DM), and mixed CTD (MCTD). 

Ye S, Chen XX, Lu XY, et al. Adult clinically amyopathic dermatomyositis with rapid progressive interstitial lung disease a retrospective cohort study. CUn Rheumatol 2007 26(10) 1647-1654. 

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