A 48-year-old HIV-positive woman presented with progressive pain and stiffness of both shoulders and hips. She was given the diagnosis of polymyalgia rheumatica (PMR) due to high erythrocyte sedimentation rate. However, a 1-week course of prednisolone failed to improve her symptoms. She later discovered a breast lump of which histopathological tissue was consistent with a diffuse large B-cell lymphoma. Whole body bone scan revealed multiple bony metastases. The presence of atypical features of PMR and lack of dramatic response to steroids should prompt physicians to raise the probability of differential diagnoses other than PMR, and in particular, malignancy.