Background: Dermatomyositis is a rare disease of multiform character. The chief anatomic features of this syndrome are nonsuppurative inflammation and degeneration of many muscles or even of the entire skeletal musculature. The condition may set in acutely, with severe and rapidly progressive symptoms, or it may appear in comparatively chronic form, with mild symptoms and sometimes with complete or partial remissions. Recently we experienced and present a patient who showed dermatomyositis. Case: 3-year old boy came to our hospital because of the all extriemitie’s weakness which occurred from the above one month ago in September 2016. The child have no trauma history. He was hard to walk and did not walk well. Whenever he sit down or stand up, he tried to hold anything sustainable. He has pain on arms, shoulders, especially both legs. Mortor exam was checked at about 4 points but has no other neurologic symtomps. Skin lesions which repeated improvement and deterioration on both knee occurred about three weeks ago . That lesions were present on interphalangeal joint of Rt. Hand at the time of admission. The nature was red, scaly, papules that erupted. In laboratory test, CK was 3,413(IU/L), LD was 1,605(IU/L), AST/ALT 134/71, and Myoglobin was 361.9(ng/mL). In addition, CK-MM was 97.70%. Extrasketal uptake was detected on whole body bone scan. Skin biopsy was conducted and it could be confirmed as gottron papule. EMG was conducted and its findings show us short duration, low amplitude as myopathic parren. TPMT gene study was conducted but could not found any abnormalities. All of these clinical and histologic findings in this patients could diagnoed as dermatomyositis. He was treated by predisol 5mg/kg/day for 13 dyas. His symptoms were improved and discharged. But because of the recurrence of symptoms he is treated by predisol and azathioprine at our OPD. And the cutaneous manifestations improved with prednisolone and azathioprine therapy in parallel with the improvement of the myositis. Conclusion: Dermatomyositis is a multisystem inflammatory disorder that is often difficult to treat, and traditional therapies. We describe a case of 3-year-old boy with DM who had clinical findings of extrimities weakness with histopathologic features of gottron’s papule and his progression.