Breast cancer in male is rare which accounts about 1% of all malignant breast neoplasm cases. Since paraneoplastic syndrome is unusual with male breast cancer, very few reported cases are found. A72- year-old gentleman presented with proximal myopathy in all four limbs was referred to Dr. Sirajul Islam Medical College and Hospital in April 2017. He had generalized wasting with reduced tone and reflexes. Planter responses were normal with intact sensory. There were typical Heliotrope rash bilaterally. In background, he had history of radical mastectomy due to stage IIA ductal carcinoma of left breast 7 years back. Three years later, he was found to have multiple metastases in lung and liver, however, deliberately discontinued chemotherapy after first dose. Currently he is on Tamoxifen. Two months back, he was diagnosed to have brain metastasis. Also his serum sodium level was low with low urine osmolality. Considering his background, we diagnosed him dermatomyositis with peripheal neuropathy & SIADH as paraneoplastic presentation of breast malignancy. Despite of normal CPK and NCV, we treated him with steroid as dermatomyositis can present with normal CPK. His myopathy improved after 2 weeks of steroid treatment. Fluid restriction increased his serum sodium level. The aim of reporting this case is to aware physicians about the aggressive nature of male breast cancer, its orthodox paraneoplastic presentation and to differentiate neuropathy from myopathy so that early treatment can improve the outcome.