Atypical mycobacterial disease: The Daily PANCE Blueprint

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Atypical mycobacterial disease: The Daily PANCE Blueprint

A 59-year-old male with a history of idiopathic pulmonary fibrosis is admitted to the hospital with an acute exacerbation of his lung disease. Physical exam is remarkable for crackles throughout both lung fields. He is placed on high-flow nasal cannula and started on daily steroids plus empiric antibiotics. A chest CT revealed new ground-glass opacities and basilar predominant honeycombing. A sputum culture is obtained and sent for bacterial, mycobacterial, and fungal cultures, along with an acid-fast bacilli smear. The sputum results with 2+ AFB but the NAAT for tuberculosis is negative. Repeat testing reveals the same result. Which of the following is the most likely diagnosis?

A. Non-tuberculosis mycobacterial infection
B. Mycobacterium tuberculosis
C. Mycoplasma pneumoniae infection
D. Both underlying bacterial and fungal infections
E. None of the above

Answer and topic summary

The answer is A. Non-tuberculosis mycobacterial infection

Atypical mycobacteria or non-tuberculous mycobacteria (NTM) are organisms that cause infections in a variety of sites (soft tissues/skin, lungs, lymph nodes, disseminated, etc). The most common NTM is Mycobacterium avium complex bacteria (MAC). These organisms are often found in environmental sources (soil, water sources, etc). People most at risk for disseminated infections include those with impaired host defenses (e.g., HIV/AIDS, patients on TNF-alpha inhibitors, CF, etc). Diagnosis is made by culturing the impacted fluid/tissue/blood, etc. Patients with pulmonary NTM will typically have positive AFB smears but negative NAAT for tuberculosis (like the patient in the question). A key point is that a positive AFB can be either TB or NTM. Treatment depends on the site but typically includes antibiotics for an extensive amount of time.

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Covered under ⇒ PANCE Blueprint Infectious Disease ⇒ Mycobacterial Disease ⇒ Atypical mycobacterial disease 

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