Dermatomyositis (DM) is an idiopathic inflammatory myopathy that associated with a variety of characteristic skin manifestations. Although DM can be easily diagnosed when pathognomic features such as heliotrope erythema and Gottron’s papules are observed, it is difficult to diagnose DM if the patient presents uncerebrated skin manifestations such as plaques like mucinosis, panniculitis and erythroderma. A 72-year-old male patient with medical history of non-small cell lung cancer and hepatocellular carcinoma referred to our dermatology clinic for ill- defined erythematous to violaceous patches on the forehead, upper back and both upper arms. Muscle weakness in both thighs and both upper arms was observed. Skin biopsy taken from forehead and back showed a few apoptotic keratinocyte and a perivascular lymphocytic infiltrate in the dermis. Alcian blue staining demonstrated abundant mucin deposits between the separated collagen bundles of both the papillary and reticular dermis. Laboratory tests showed elevation of creatinine kinase and myoglobin, lactate dehydrogenase. Muscles biopsy revealed the inflammation between the muscles cells and abnormal muscle cell degeneration. From these findings, the diagnosis of DM was made. Herein, we report a educative case of DM that associated with atypical cutaneous findings of mucinosis presenting as a non specific violaceous patches.