Abstract: Dermatomyositis is a rare autoimmune inflammatory myopathy with proximal muscle weakness and skin affection. Only 4 cases of HIV that subsequently developed dermatomyositis have been reported. This is the first case of dermatomyositis being the initial presentation of an acute seroconversion illness. We highlight the pathophysiology of dermatomyositis in HIV infection along with the complex issues of treatment in such cases. We report a case of a 50-year-old woman who presented with a 2 months’ history of proximal muscle weakness with classic signs of dermatomyositis and consistent electromyographic and muscle biopsy. HIV (by enzyme-linked immunosorbent assay) was initially nonreactive, indeterminate at 4 weeks, and positive at 8 weeks. It was further confirmed by Western blot and polymerase chain reaction. She was treated with prednisolone and antiretroviral therapy. A high degree of suspicion is required to diagnose HIV seroconversion when an individual presents with dermatomyositis. A fine balance of immunosuppressants and antiretroviral therapy needs to be maintained in the treatment of such cases.