A 25-year-old man comes to the emergency department due to 3 weeks of progressive dyspnea on exertion, dry cough, fatigue, intermittent fever, and chills. He was treated for genital herpes several years ago but otherwise has no significant medical history. The patient does not use tobacco or illicit drugs but occasionally drinks alcohol. He has been in a monogamous relationship for the past year and had multiple partners previously. Temperature is 38.7 C (101.7 F), blood pressure is 130/80 mm Hg, pulse is 90/min, and respirations are 28/min. Pulse oximetry is 88% on room air. Scattered white plaques are present on the oropharyngeal mucosa. Lung auscultation reveals bilateral, diffuse crackles. Chest x-ray is shown in the image below. Arterial blood gas shows a PaO₂ of 60 mm Hg and a PaCO₂ of 33 mm Hg. Induced sputum microscopy shows few leukocytes and no predominant organism. Which of the following is most likely to be effective for this patient's pulmonary condition?

Question

Quizplus · Accepted Answer

11ec25c8_d467_2944_bc81_51176b51c049_MD0003_00 This patient's history of multiple sexual partners and evidence of oropharyngeal thrush (white mucosal plaques) raise strong suspicion for underlying HIV infection. The presence of subacute pulmonary symptoms (dyspnea, dry cough, fever), tachypnea, hypoxemia, and bilateral interstitial infiltrates on chest x-ray indicates likely Pneumocystis pneumonia (PCP), a common harbinger of AIDS in patients previously unaware of HIV infection. Most cases arise when CD4 counts are <200/mm³. chest x-ray Manifestations typically build over weeks and include progressive dyspnea, dry cough, and fever. Chest x-ray frequently reveals bilateral pulmonary reticulonodular infiltrates. Diagnosis requires the identification of organisms in respiratory secretions using microscopy with specialized stains. Induced sputum often provides adequate samples, but bronchoscopy with bronchoalveolar lavage is required when induced sputum cannot be obtained or is unrevealing (as in this case). Trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line treatment for PCP. Patients with mild or moderate disease are treated with oral TMP-SMX, whereas those with more severe disease (eg, large alveolar-arterial gradient, low PaO₂, tachypnea) often require intravenous therapy. Because TMP-SMX may transiently worsen pulmonary function (likely due to the inflammatory effects of lysed organisms), concomitant corticosteroids (eg, prednisone) are administered to patients with severely impaired oxygenation. This includes those with pulse oximetry <92%, PaO₂ ≤70 mm Hg, or alveolar-arterial gradient ≥35 mm Hg on room air. Antiretroviral therapy should also be initiated within 2 weeks (once hypoxia improves) to prevent AIDS progression. (Choices A and E) Ceftriaxone with azithromycin is used to treat community-acquired pneumonia (CAP), and vancomycin with piperacillin-tazobactam is used to treat hospital-acquired pneumonia (HAP). Both CAP and HAP tend to cause acute illness (within hours or days), productive cough, and lobar infiltrates on chest x-ray. Although CAP due to an atypical organism (eg, Mycoplasma) can sometimes cause subacute, nonproductive cough and interstitial infiltrates, patients usually have mild illness; significant dyspnea/hypoxia and high fever would be atypical. (Choice B) Isoniazid, rifampin, pyrazinamide, and ethambutol are used to treat tuberculosis, which tends to present with fever, hemoptysis, and weight loss. Chest x-ray usually reveals apical, cavitary infiltrates. This patient has bilateral interstitial infiltrates, making PCP more likely. (Choice C) Liposomal amphotericin B is used to treat severe fungal infections (eg, histoplasmosis, cryptococcal meningitis). Pulmonary histoplasmosis usually causes focal or perihilar infiltrates (not diffuse interstitial infiltrates) on chest x-ray. Amphotericin B is not commonly used in the treatment of PCP. Educational objective: Pneumocystis pneumonia is common in patients with advanced AIDS (CD4 counts <200/mm³). Trimethoprim-sulfamethoxazole is the first-line treatment; concomitant corticosteroids are added for those with pulse oximetry <92%, PaO₂ ≤70 mm Hg, or alveolar-arterial gradient ≥35 mm Hg on room air to reduce risk of worsened hypoxia with treatment initiation. References: Pneumocystis pneumonia: current concepts in pathogenesis, diagnosis, and treatment. (http://www.ncbi.nlm.nih.gov/pubmed/19375633)

A 25-Year-Old Man Comes to the Emergency Department Due to 3