MAC/MAI .. just ONE article I have come across that I felt might help Newcomers in understanding their diagnosis of MAC/MAI .. a LOT of information to digest but I hope you find it helpful! Hugs! Katherine (I have left out information on Aids .. for most of our arriving Newcomers that has not been an issue.)
https://patient.info/doctor/mycobacterium-avium-complex Synonyms: Mycobacterium avium-intracellulare, MAI There are two discrete species in the Mycobacterium avium complex (MAC): Mycobacterium avium (M. avium). Mycobacterium intracellulare (M. intracellulare). They are both opportunistic pathogens that affect the immunocompromised. They can affect immunocompetent people, especially those with pre-existing lung disease. MAC is ubiquitous. However, only a minority of people exposed to MAC will acquire infection. It usually only affects the lungs in the immunocompetent.
Pathophysiology M. intracellulare causes 40% of MAC infections in the immunocompetent. Transmission is via the respiratory (inhalation) and the gastrointestinal (ingestion) routes. There are many environmental sources of MAC including: Piped hot water systems (household and hospital). Aerosolised water (eg, hot tubs). House dust. Soil. Birds and farm animals. Tobacco, cigarette filters and paper. In those with pre-existing lung disease, MAC usually just leads to pulmonary infection. The infection may (rarely) appear in elderly ladies with no pre-existing lung disease who chronically suppress the cough reflex and therefore allow respiratory secretions to stagnate. This is known as Lady Windermere syndrome. MAC can also present as a hypersensitivity pneumonitis. This can occur in those exposed to water vapour containing MAC (commonly in poorly maintained indoor hot tubs or swimming pools). Risk factors immunosuppression. Bronchiectasis. Cystic fibrosis. Chronic obstructive pulmonary disease (COPD). Pulmonary malignancy.
Presentation Pulmonary MAC infection Insidious onset. Features include: Cough. Excessive sputum production. Dyspnoea (difficult or labored breathing). Haemoptysis (coughing of blood). Fever and night sweats. Fatigue. Weight loss. Nonspecific focal chest signs: crackles, wheeze, bronchial breathing, dullness to percussion. Clubbing (in cases with underlying bronchiectasis).
Disseminated MAC infection ..] Features include: Fever (may present as pyrexia of unknown origin). Sweating. Malaise. Dyspnoea (difficult or labored breathing). Diarrhoea. Significant weight loss with marked wasting. Generalised lymphadenopathy (disease of the lymph nodes) Pallor. Tender hepatosplenomegaly (disorder where both the liver and spleen swell beyond their normal size) Cutaneous involvement.
• Sputum AFB staining: this is positive in most with MAC.
• Sputum culture: takes 1-2 weeks to detect the organism but doesn’t differentiate between infection or just colonisation. A number of positive cultures are usually required for diagnosis and there are set criteria.
• CXR: may show cavitary changes, nodules and parenchymal involvement, particularly in middle and upper lobes, and mediastinal lymphadenopathy.
• CT scan of the chest: this may be needed to show lung involvement.
• Bronchoscopy and transbronchial biopsy/CT-guided needle biopsy: this may be needed to make the diagnosis. There are specific histological changes in the lung tissue. Last Checked: 29 August 2014