A 43-year-old man undergoes induction chemotherapy for acute myeloid leukemia. Three weeks later, he is hospitalized with fever, cough, and generalized weakness. On physical examination, his temperature is 38.1 C (100.7 F), blood pressure is 102/68 mm Hg, and pulse is 125/min. The patient's pulse oximetry shows 95% on room air. Crackles are heard over the right upper lung. His hemoglobin level is 9.5 g/dL, and leukocyte count is 900/mm³ with an absolute neutrophil count of 100/mm³. Chest x-ray reveals a dense infiltrate involving the right upper lung lobe. Broad-spectrum antibiotic therapy is instituted. Five days later, the patient is still febrile. Bronchoscopy with biopsy is performed and the tissue samples from the bronchoscopy grow mold. Which of the following organisms is most likely responsible for this patient's current condition?

Question

Quizplus · Accepted Answer

This patient with leukemia recently underwent chemotherapy (with likely myelosuppressive effects) and now has a fungal respiratory infection with febrile neutropenia (FN), typically defined as fever with an absolute neutrophil count <500/mm³. Patients with FN are at increased risk for severe infection. Broad-spectrum antibiotic therapy is indicated. Gram-positive bacteria are the most commonly identified pathogens in FN followed by gram-negative organisms. However, patients with profound and prolonged neutropenia (several days) are at especially high risk for fungal infections. Invasive pulmonary aspergillosis presents with some combination of fever, chest pain, cough, dyspnea, and hemoptysis. Chest imaging can show diffuse consolidation, nodules, or cavitary lesions. On light microscopy, Aspergillus is seen as septate narrow hyphae that branch at a 45° angle. Antifungal therapy is needed. (Choice B) Candida is another common fungal infection in patients with FN. However, isolated respiratory infection due to Candida is very uncommon; candidemia typically manifests with fever and other nonspecific findings, although erythematous skin nodules develop in some patients. (Choice C) Cryptococcus neoformans is a yeast that most frequently causes opportunistic infections in patients with immunosuppression, especially those with HIV/AIDS. The most common presentation is meningoencephalitis. (Choice D) Pneumocystis pneumonia (PCP) is an important cause of severe respiratory infection in immunocompromised patients. PCP can present with fever and cough, but chest radiographs most commonly reveal diffuse, bilateral interstitial infiltrates. Pneumocystis cannot be cultured but can be visualized microscopically in bronchoalveolar lavage, sputum, and tissue specimens. (Choice E) Rhizopus infection can lead to mucormycosis, which most commonly presents with a sinus infection that spreads rapidly to involve the orbits and brain (classically seen in patients with diabetes). Educational objective: Patients with profound and prolonged neutropenia are at especially high risk for fungal infections. The most common fungal causes are Aspergillus and Candida species. Invasive pulmonary aspergillosis presents with some combination of fever, chest pain, cough, dyspnea, and hemoptysis. __________ References: Pulmonary aspergillosis: clinical presentation, diagnostic tests, management and complications. (http://www.ncbi.nlm.nih.gov/pubmed/20375786) Pulmonary aspergillosis: a clinical review. (http://www.ncbi.nlm.nih.gov/pubmed/21881144)

A 43-Year-Old Man Undergoes Induction Chemotherapy for Acute Myeloid Leukemia