A 34-year-old man comes to the emergency department due to 3 weeks of fever, night sweats, fatigue, cough, and shortness of breath. He has lost 4.5 kg (10 lb) over this period. The patient was diagnosed with HIV a year ago but is not taking antiretroviral medication. His CD4 count was 80/mm³ 3 months ago. The patient is unemployed and recently moved to Missouri to live with his parents. He does not use tobacco, alcohol, or illicit drugs. Temperature is 38.5 C (101.3 F) , blood pressure is 110/66 mm Hg, and pulse is 108/min. There are small ulcers on the hard palate and multiple enlarged lymph nodes in the cervical and inguinal chains. Pulmonary examination reveals scattered lung crackles. The patient's abdomen is soft and nontender, but there is prominent hepatosplenomegaly. Laboratory studies show pancytopenia and elevated aminotransferase levels. Chest x-ray reveals bilateral reticulonodular opacities with hilar lymphadenopathy.
Which of the following is the best next step in management of this patient?

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11ec25c8_d455_27c5_bc81_033edf329e5d_MD0003_00 Histoplasma capsulatum is an endemic mycosis of the central and midwestern United States that proliferates in soil contaminated by bird or bat droppings. Most infections are asymptomatic in immunocompetent individuals (<5% develop pulmonary or disseminated disease). However, patients with defects in cell-mediated immunity, such as those with advanced HIV (CD4 <100/mm³), are far more likely to develop progressive disseminated histoplasmosis (PDH) (>90%). PDH is marked by the spread of H capsulatum from the lungs through the lymph to the systemic circulation with resulting unchecked multiorgan infection. Patients develop a febrile, wasting disorder with prominent pulmonary (dyspnea, cough), mucocutaneous (papules, nodules), and reticuloendothelial (lymphadenopathy, hepatosplenomegaly) manifestations. Laboratory examination often shows pancytopenia (due to bone marrow infiltration) and elevated aminotransferase/lactate dehydrogenase levels. Many patients have diffuse interstitial or reticulonodular infiltrates on chest x-ray (as the lungs are the portal of entry). Diagnosis is confirmed most rapidly with serum or urine Histoplasma antigen immunoassay (sensitivity >95%). (Choice A) Pneumocystis pneumonia (PCP) is a common opportunistic infection in advanced HIV marked by subacute pulmonary symptoms (often with hypoxia) and fever. Patients with suspected PCP who have negative induced sputum samples often receive bronchoscopy with bronchoalveolar lavage. PCP does not commonly cause lymphadenopathy, hepatosplenomegaly, or pancytopenia. (Choice B) Most patients with suspected histoplasmosis receive fungal blood cultures; however, culture results usually take 4-6 weeks for incubation. Therefore, urine or serum Histoplasma antigen is the test of choice for diagnosis (highly sensitive and rapid). (Choice C) A biopsy of an enlarged lymph node is rarely required to diagnose histoplasmosis. Disseminated tuberculosis (which can be diagnosed by lymph node biopsy) could explain many of this patient's findings; however, cutaneous lesions are uncommon, and the combination of pulmonary, mucocutaneous, and reticuloendothelial findings in the correct epidemiologic setting (eg, recent move to Missouri) make PDH more likely. (Choice D) Syphilis may cause subacute febrile symptoms combined with mucocutaneous lesions. Pulmonary involvement and pancytopenia are uncommon. Educational objective: Histoplasma capsulatum rarely causes illness in immunocompetent patients; however, in patients with advanced HIV (CD4 <100/mm³), progressive disseminated histoplasmosis (PDH) is the norm (>90%). Urine or serum Histoplasma antigen assay is a rapid, sensitive test for diagnosing PDH. References: Diagnosis of histoplasmosis in immunosuppressed patients. (http://www.ncbi.nlm.nih.gov/pubmed/18594296)

A 34-Year-Old Man Comes to the Emergency Department Due to 3