Cases from the Osler Medical Service at Johns Hopkins University.

PRESENTING FEATURES: An 18-year-old white man was admitted to the Osler Medical Service with the chief complaint of back pain. Two weeks prior to admission, the patient developed diffuse and aching upper back pain. Over the next couple of days, he also developed severe anterior chest pain that was somewhat pleuritic in nature but diffuse and extending bilaterally into the shoulders. One week prior to admission, he developed intermittent fevers and night sweats. The patient denied any lymphadenopathy, pharyngitis, sick contacts, shortness of breath, rash, or bleeding. He was seen by a physician and told that he had thrombocytopenia. There was no history of recent or remote unusual bleeding episodes. His medical history was unremarkable except for a childhood diagnosis of attention deficit/hyperactivity disorder. He was not taking any medications and had no history of tobacco, alcohol, or illicit drug use. He had no risk factors for human immunodeficiency virus infection. Physical examination showed that he was afebrile and had normal vital signs. He was a well-appearing man who was lying still because of pain. HEENT examination was unremarkable. There was no pharyngeal erythema or exudates. His lungs were clear. His neck was supple and without lymphadenopathy. Examination of his back and chest revealed no focal tenderness. There was no hepatosplenomegaly, and his skin was without petechiae or rashes. Examination of the patient's joints showed pain on passive and active movement of his shoulders bilaterally, but no frank arthritis. There was no rash, petechiae, or echymoses. Chest radiograph and electrocardiogram were unremarkable. On admission, the laboratory examination was notable for a hematocrit level of 32.5%, with a mean corpuscular volume of 79 fL, and white blood cell count of 2.8 x 10(3)/microL. Platelet count was 75 x 10(3)/microL. A white blood cell differential revealed 7% bands, 53% polys, 34% lymphs, 5% atypical lymphocytes, 2% nucleated red cells, and a few young unidentified cells. His chemistry studies were unremarkable. What is the diagnosis?