An 84-year old man was admitted to Mitoyo General Hospital because of progressive malaise and edematous erythema on both eyelids (Heliotrope erythema). He also noted blister on his neck as well as erythema on the extensor surface of finger joints (Gottron's sign), elbows and knees. Neither weakness nor pain of his proximal muscle was elicited on physical examination on admission. His blood test disclosed positive inflammatory signs (i.e., mild elevation of ESR and positive CRP) without elevated value of muscle enzymes. Electromyogram showed normal pattern. Infiltration of inflammatory cells was not revealed by histological examination of biopsied muscle. A diagnosis of 'amyopathic dermatomyositis' was made based on these observations. Computed tomography of his chest disclosed interstitial pneumonia spreading over both lower lung fields. Colon fiberscopy revealed a polyp in his descending colon, which was classified into group I on cytological examination. He was treated with two sets of methylprednisolone (mPSL) pulse therapy (500 mg/day, 3 consecutive days, intravenously) followed by 30 mg/day of oral prednisolone (PSL). His skin lesions responded well to the above treatment and the dose of oral PSL was tapered. One month after the initiation of treatment, severe stomatitis as well as a large ulcer beneath his tongue developed accompanying an intractable pain. Mucosal biopsy revealed necrotizing vasculitis in medium-sizedartery at the bottom of ulcer. Another set of mPSL pulse therapy brought a prompt relief of his symptom and prohibited the recurrence of oral lesion. It should be noted that our patient did not fulfill the diagnostic criteria for DM because of the lack of muscular symptoms whereas he had characteristic skin lesions. Regarding the frustration possibly encountered at the time of diagnosing amyopathic DM, both sensitivity and specificity of the skin lesion for the diagnosis of DM were investigated. Moreover, the rarity of blister as a skin manifestation of DM was discussed as well.