A 27-year-old HIV-positive man comes to the emergency department with shortness of breath, dry cough, and right-sided chest pain since yesterday. The chest pain is worse when he takes a deep breath or coughs. He has had chills and night sweats for the last week, which he has attributed to the flu. The patient has been hospitalized for opioid overdose several times in the past. Four months ago, he was admitted and treated for aspiration pneumonia. Last year he was hospitalized for cocaine overdose complicated by tonic-clonic seizures. His most recent CD4 lymphocyte count was 190/mm³ 2 months ago. He has no drug allergies. In the emergency department he appears mildly uncomfortable and has shallow breathing. Temperature is 39.4 C (103 F), blood pressure is 100/70 mm Hg, pulse is 110/min and regular, and respirations are 22/min. BMI is 19 kg/m². Pulse oximetry is 95% on room air. There are multiple needle tracks and a painful subcutaneous mass in the right antecubital area. The neck veins are flat with the patient in semi-recumbent position. There is a 2/6 systolic murmur heard at the left sternal border. The liver is palpated 1 cm below the costal margin and is nontender. Chest x-ray reveals nodular opacities in both lung fields, including subpleural opacities on the right. Serum potassium is 3.8 mg/dL and creatinine is 1.1 mg/dL. Blood cultures are obtained and intravenous fluids are initiated. Which of the following is most likely to establish the diagnosis in this patient?

Question

Quizplus · Accepted Answer

Explanation: This patient most likely has acute right-sided infective endocarditis (IE) and should undergo transthoracic echocardiography to establish the diagnosis. Intravenous drug users are at increased risk of developing IE, and HIV infection further increases the risk, especially with low CD4 lymphocyte count. Although left-sided IE is more common in the general population, intravenous drug users most commonly develop right-sided IE affecting the tricuspid valve. The propensity for right-sided IE may relate to injected particulate matter causing damage to the tricuspid valve (allowing for bacterial adherence) before being filtered out by the pulmonary capillaries (therefore never reaching the mitral or aortic valve). Staphylococcus aureus is responsible for >50% of cases of IE in intravenous drug users; the presentation is typically acute and characterized by high fever. Patients often have pleuritic chest pain and cough due to septic pulmonary emboli, a complication that occurs in 75% of cases of right-sided IE. The emboli appear on chest x-ray as multiple nodular opacities that may have evidence of cavitation. Cardiac murmur is sometimes absent in right-sided IE, and peripheral signs of IE (eg, splinter hemorrhages, Janeway lesions) are usually absent. The painful subcutaneous nodule in this patient's antecubital region represents septic thrombophlebitis (a clue to intravenous drug use) rather than a peripheral manifestation of IE. (Choices A and C) This patient who is HIV positive with a low CD4 lymphocyte count (<200/mm³) is at risk for Pneumocystis pneumonia. Sputum induction or bronchoscopy with lavage is used for diagnosis; however, the presentation in patients with HIV is typically subacute (eg, 3 weeks of low-grade fever and nonproductive cough) rather than acute, and chest x-ray typically reveals interstitial infiltrates rather than nodular opacities. (Choice B) CT angiography of the chest is used to diagnose pulmonary embolism, which may cause pulmonary infarct appearing as subpleural opacity on chest x-ray. However, multiple bilateral infarcts are unlikely, and this patient's high fever and intravenous drug use make septic emboli from right-sided IE more likely. (Choice E) Urine antigen testing is useful in diagnosing Legionella pneumonia. The infection is often characterized by high fever; however, accompanying gastrointestinal symptoms (eg, vomiting, diarrhea) are often present and chest x-ray typically reveals unilobar consolidation rather than multiple discrete opacities. Educational objective: Intravenous drug users are at increased risk for infective endocarditis that is most commonly right-sided and involves the tricuspid valve. Echocardiography (transthoracic initially, followed by transesophageal if needed) is used for diagnosis. References: Tricuspid endocarditis and septic pulmonary embolism in an intravenous drug user with advanced HIV infection. (http://www.ncbi.nlm.nih.gov/pubmed/22125735) Tricuspid valve endocarditis complicated by septic pulmonary embolism in an intravenous drug user. (http://www.ncbi.nlm.nih.gov/pubmed/24078456) Human immunodeficiency virus infection and infective endocarditis among injecting drug users. (http://www.ncbi.nlm.nih.gov/pubmed/8899380)

A 27-Year-Old HIV-Positive Man Comes to the Emergency Department with Shortness