An extremely rare case of acute inflammatory myopathy during combination chemotherapy with docetaxel and carboplatin for metastatic breast carcinoma in a 62-year-old diabetic female patient is reported. Despite the early clinical partial response of the underlying malignancy to the chemotherapeutic regimen, the patient developed symmetrical, painful, proximal muscle weakness in the lower limbs with peripheral edema after the administration of the third cycle of treatment. The syndrome regressed after the discontinuation of chemotherapy and the administration of corticosteroids.