Focal myositis is a very rare form of inflammatory myopathy, with unknown etiology. We describe a 44-year-old previously healthy man who noticed a painless swelling on his left forearm, following trauma over the left cubital fossa. The swelling grew progressively over 2 years. He had otherwise no weakness complaints. Physical and neurological examinations were otherwise normal. Creatine kinase and aldolase levels were increased (1,009 U/L and 11.9 U/L, respectively); autoimmunity panel was negative. MRI showed diffuse edema and gadolinium enhancement of muscles innervated by the median nerve. EMG revealed repetitive complex discharges and patterns of continuous muscular activity. The mass was biopsied disclosing findings consistent with focal myositis. Focal myositis with muscular atrophy is a rare situation; the inflammatory mechanism is yet to be defined, but it seems to be a situation with slow progression, with tendency to stabilization. .