Chief complaint: Right hand and arm rash. History of present illness:A 31-year-old. right-handdominant, ivhite male office worker presents for evaluation of multiple clusters of erythematous papules on the dorsum of his right hand. H e states that the lesions began as an isolated nodule three months prior to this evaluation. He did not seek medical attention initially. and treated the lesions with soap. water. and cortisone cream. However, when the nodules increased in size and additional nodules appeared. the patient sought the advice of his family physician. who placed the patient on cefadroxil. After completion of a two-week course of treatment. the lesions increased in number and gradually spread proximally to his axilla.Constitutional symptoms, including fevers, chills, night sweats. productive or nonproductive cough, fatigue. and weight loss, are absent. The patient denies risk factors for immunosuppressive disorders. The patient takes no other medication and has no history of drug allergies. Further discussion reveals that his hobbies include keeping and caring for three tanks of tropical fish. Physical examination:The patient is in n o acute distress. His vital signs are normal. Examination of the dorsum of the right hand reveals multiple clusters of nontender. indurated papules on erythematous bases (Fig. 1). N o swelling. warmth. or drainage is noted. The right volar I FlGURE I . The patient's hand on ED presentation forearm contains multiple. discrete. erythematous. nontender, nonfluctuant. subcutaneous nodules approximately 1 cm in diameter. Several erythematous, nontender, fluctuant. subcutaneous nodules larger than those on the forearm are seen on the proximal aspect of the right arm. No axillary adenopathy is noted, although superficial phlebitis with palpable cords cover5 the entire arm.Laboratory and additional tests: Radiographs of the right upper extremity reveal only soft-tissue swelling. A procedure is performed and the patient is scheduled for follow-up.