Mycobacterium avium complex (MAC) has variable presenting features including chronic cough, weight loss, and fevers.
Increased incidence in patients with underlying lung disease, heavy smoking, and excessive alcohol consumption.
HIV-infected patients with CD4 cell count <50 cells/microlitre also at increased risk of infection.
Diagnosis of pulmonary disease in non-HIV-infected individuals requires repeated isolation of the organism from respiratory secretions, in addition to compatible symptoms and radiographical presentation.
Combination treatment with at least two drugs is essential.
Mycobacterium avium complex (MAC), also known as mycobacterium avium-intracellulare (MAI), consists of two mycobacterium species, M avium and M intracellulare. Although MAC isolates can be identified as M avium or M intracellulare by molecular techniques, there is no prognostic or treatment advantage for doing so. In humans, MAC traditionally causes three disease syndromes: pulmonary disease, cervical lymphadenitis, and disseminated disease. A fourth syndrome, a hypersensitivity pneumonitis associated with hot tub use, has also been described.
History and exam
Key diagnostic factors
- underlying lung disease
- chronic productive cough
- weight loss
- hot tub use
Other diagnostic factors
- age under 5 years
- middle-to-old age
- night sweats
- abdominal pain
- thin body habitus
- pectus excavatum
- systolic click and murmur
- underlying lung diseases
- excessive alcohol use
- older men
- post-menopausal women
- hot tub use
- severe immunosuppression
- genetic cytokine defects
1st investigations to order
- FBC with differential
- chest x-ray
- sputum culture
- blood culture
Investigations to consider
- high-resolution CT (HRCT) scanning
- bone marrow aspirate for culture
- bronchoscopy/bronchial lavage
- lung biopsy
- lymph node biopsy
- polymerase chain reaction
MAC hypersensitivity pneumonitis
Zelalem Temesgen, MD, FIDSA
Professor of Medicine
Director, Mayo Clinic Center for Tuberculosis – A World Health Organization – Collaborating Center in Digital Health and Precision Medicine
Director, HIV Program
Consultant, Division of Infectious Diseases
ZT declares that he has no competing interests.
Dr Temesgen would like to gratefully acknowledge Dr Dereje S. Ayo, a previous contributor to this topic.
DSA declares that he has no competing interests.
Jonathan P. Parsons, MD
Division of Pulmonary, Allergy, Critical Care and Sleep Medicine
Ohio State University Medical Center
JPP declares that he has no competing interests.
Sandro Vento, MD
Infectious Diseases Unit
SV declares that he has no competing interests.
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