Snapshot A 32-year-old man presents to the ED with a two week history of fever and dry cough. For the past five days, he has been having shortness of breath. There is no history of pleuritic chest pain or rigors. Past surgical history reveals the patient had an adrenelectomy two years ago and is on dexamethasone. His temperature is 100.4°F (38°C), pulse is 92/min, O2 saturation is 92%, respirations are 18/min, and blood pressure is 120/70 mmHg. Chest exam reveals bibasal crackles. Chest radiograph shows interstitial infiltrates bilaterally. The patient's condition worsens on levofloxacin. Bronchoscopic lavage was carried out and a stain of the sample is seen on the right. Introduction Classification opportunistic fungi P. jiroveci (formerly P. carinii) Pathogenesis inhaled kills type I pneumocytes type II pneumocytes overreplicate and damage alveolar epithelium fluid leaks into alveoli producing an exudate seen as honeycomb appearance on H&E Presentation "PCP" ("P. carinii" pneumonia) diffuse interstitial pneumonia fever cough dyspnea on exertion tachypnea weight loss fatigue impaired oxygenation seen in immunosuppressed especially AIDS especially CD4 < 200 cells/mm3 malnourished or premature babies Evaluation WBC count typically normal ABG shows low PaO2 CXR diffuse bilateral interstitial infiltrates ground-glass appearance however, may present atypically Definitive diagnosis with lung biopsy or lavage methenamine silver stained cysts seen in tissues Differential TB Histoplasmosis Coccidioidomycosis Treatment Antibiotics TMP-SMX high dose x21 days if sulfonamide allergy atovaquone pentamidine dapsone Prophylaxis treated prophylactically in transplant patients and HIV patients with CD4 < 200 cells/mm3 Steroids if hypoxic prednisone if PaO2 < 70 mmHg A-a gradient > 35 mmHg HAART start HAART 14 days after initiating treatment of PCP, if not already taking Prognosis, Prevention, and Complications Prevention prophylaxis with TMP-SMX give dapsone or atovaquone in sulfa allergy indications HIV patients with CD4 < 200 cells/mm3 oropharyngeal candidiasis patient on > 20mg/day of steroids for one month or greater