Case 84 | Clinical Pathology Unknown Conference

1. Presented by Matthew Gabrielson, MD and reviewed by Nicole Parrish, PhD

Clinical Vignette

An elderly patient with a past medical history of congestive heart failure and chronic obstructive pulmonary disease (COPD) presents to the emergency room with increased at home oxygen requirement and acute onset shortness of breath. Aside from shortness of breath, review of systems is negative, and they decline fevers, chest pain, new sputum production, sick contacts, cough, and other respiratory symptoms. Further questioning reveals the patient received a lung lobectomy for a tuberculosis infection decades ago. Current medications include furosemide, lovastatin, ipratropium, tiotropium, and albuterol (inhaler). Vital signs are within normal limits. The initial infectious workup is notable for a normal WBC count (4.5, 61.2% PMNs) and negative Influenza A/B, RSV and COVID19 PCRs. CT Chest reveals a cavitary mass in the right lung apex (see Figure A). The patient is hospitalized for management of this lung lesion, but a broad infectious workup for numerous infectious organisms, including Mycobacterium tuberculosis, is negative. Approximately 6 weeks after the initial induced sputum sample was collected, the mycobacterial culture returned positive for growth (see Figure B).

Figure A: CT chest demonstrating a cavitary mass in the right lung apex

Figure B: Growth of the organism on Lowenstein-Jensen (LJ) medium

Question:
Which of the following organisms is likely responsible for this patient's clinical presentation?

A. Mycobacterium tuberculosis

B. Mycobacterium avium complex (MAC)

C. Mycobacterium kansasii

D. Mycobacterium leprae

E. Streptococcus pneumoniae

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