An 82-year-old African-American female was brought from nursing home after she complained of vague abdominal discomfort for 1 day. She had no nausea, vomiting, shortness of breath, cough, night sweats, fever, appetite change, or weight loss. The review of symptoms was otherwise unremarkable. Her past medical history included dementia, diabetes mellitus, and hypertension. On admission, her blood pressure was 92/63 mm Hg, pulse rate was 83 bpm, temperature was 97  F, respiratory rate was 19/min, and oxygen saturation was 99% on room air. Physical examination revealed reduced air entry with fine crepitation on right lung base, mild abdominal distension, and diffuses tenderness with no guarding, rigidity, or rebound tenderness. Laboratory findings were significant for hemoglobin of 11.2 gm/dl, blood urea nitrogen level of 38 mg/dl, serum creatinine of 1.6 mg/dl, blood glucose of 393 mg/dl, amylase of 115 mg/dl, and serum albumin of 2.8 gm/dl. White blood cell count, serum lipase, ketones, and lactic acid levels were normal. Blood cultures showed no growth. Computed tomography (CT) scan of abdomen and pelvis revealed retained fecal material in the colon, non-obstructing left renal calculus, and bilateral small pleural effusion with right-sided lung infiltrates. The patient was managed for constipation and suspected pneumonia, and was started on ceftriaxone and azithromycin. Subsequent CT scan of the chest (Figure 1) showed 4.5 cm pleural-based opacity in right lung base with a small cavity, patchy ground-glass opacity in right upper and right middle lobe along with bibasilar subsegmental atelectasis. Antibiotics were discontinued after 2 days as clinical suspicion of bacterial pneumonia was low. She was placed on airborne isolation. Subsequently, sputum smear for acid-fast bacilli was positive. Mycobacterial culture reported positive growth of M. nebraskense, while polymerase chain reaction returned negative for Mycobacterium gordonae,  M. kansasii, MAC, and Mycobacterium tuberculosis. With the patient asymptomatic and her constipation improved with laxatives, she was discharged with plans for close follow-up as outpatient.
Chest CT scan reveals right lower lobe cavity.