A 53 year-old woman presented with four months of weakness and a rash. The weakness was progressive, symmetric, and proximal. The muscles of both her upper and lower extremities were affected. The erythematous rash was located on the inner thighs and arms bilaterally. She could not raise her arms and had difficulty holding her head erect; her leg weakness prohibited standing independently. Sensation and reflexes were not affected. She had normal serum electrolytes and complete blood count. Her AST was 200 U/L, ALT 78 U/ L, ALKP 52 U/L, CK 7021U/L, and ESR 29 mm/hr. Her TSH, hepatitis panel, ANA, rheumatoid factor, anti-DS DNA, c-ANCA, and p-ANCA were normal. A muscle biopsy of left thigh showed vasculitis and perifascicular atrophy and necrosis. Methylprednisolone and methotrexate were initiated with resolution of her symptoms. An age-appropriate screen for cancer was negative. IMPLICATIONS/DISCUSSION: The diagnosis of dermatomyositis/polymyositis (DM/PM) requires a high degree of clinical suspicion, as it is established based on the combination of clinical, laboratory, and muscle biopsy findings. This patient demonstrated the proximal muscle weakness characteristic of DM/PM. Other causes of proximal muscle weakness, including electrolyte abnormalities, hypothyroidism, inclusion body myositis or drug induced (HMG CoA reductase inhibitors or steroids) were excluded by history and laboratory data. Perifasicular inflammation suggests dermatomyositis; perimysial inflammation is characteristic of drug-induced myositis. Diagnostic criteria for dermatomyositis include symmetric proximal muscle weakness, elevated serum muscle enzymes, perifasicular inflammation on muscle biopsy, and rash. The classic dermatologic findings of PM/DM include mechanic's hands (synthetase AB subset), heliotrope lids, Gottron's sign and shawl sign . Physicians should be aware that most cases of DM/PM present without the classic findings of DM/PM. Systemic corticosteroids are used for treatment. Immunosuppressive agents are used in cases refractory to corticosteroid treatment. Due to an association with underlying malignancy, an age and gender appropriate cancer screen should be performed in all patients diagnosed with dermatomyositis.