Mycobacterium avium complex: Difference between revisions
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Mycobacterium avium complex
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= Microbiology = |
== Microbiology == |
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* A slow-growing [[Non-tuberculous mycobacteria (NTM)|non-tuberculous mycobacterium]] |
* A slow-growing [[Non-tuberculous mycobacteria (NTM)|non-tuberculous mycobacterium]] |
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* Can colonize airways and GI tract as well as causing disease |
* Can colonize airways and GI tract as well as causing disease |
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= Differential Diagnosis = |
== Differential Diagnosis == |
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* Pulmonary disease |
* Pulmonary disease |
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** ''M. abscessus'' |
** ''M. abscessus'' |
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= Epidemiology = |
== Epidemiology == |
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* Common in the environment, likely acquired by inhalation or ingestion (not person-to-person) |
* Common in the environment, likely acquired by inhalation or ingestion (not person-to-person) |
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** Cervical lymphadenitis: children 1-5 years old, HIV with IRIS |
** Cervical lymphadenitis: children 1-5 years old, HIV with IRIS |
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= Pathophysiology = |
== Pathophysiology == |
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* In pulmonary disease, likely inhalation ± microaspiration |
* In pulmonary disease, likely inhalation ± microaspiration |
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* In disseminated disease in AIDS, likely GI colonization then replication and dissemination |
* In disseminated disease in AIDS, likely GI colonization then replication and dissemination |
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= Clinical Presentation = |
== Clinical Presentation == |
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== Pulmonary disease == |
=== Pulmonary disease === |
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* Incubation months to years |
* Incubation months to years |
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** Hot tub lung disease: a hypersensitivity pneumonitis associated with inhalation |
** Hot tub lung disease: a hypersensitivity pneumonitis associated with inhalation |
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== Disseminated disease == |
=== Disseminated disease === |
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* Almost exclusive to HIV patients with CD4 <100 |
* Almost exclusive to HIV patients with CD4 <100 |
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* Mortality 50% at 4 months |
* Mortality 50% at 4 months |
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== Cervical lymphadenitis == |
=== Cervical lymphadenitis === |
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* Disease of children, usually <3 (80% aged 1 to 5 years) |
* Disease of children, usually <3 (80% aged 1 to 5 years) |
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** 10% bilateral |
** 10% bilateral |
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= Investigations = |
== Investigations == |
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== Pulmonary disease == |
=== Pulmonary disease === |
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* (1) chest radiograph or, in the absence of cavitation, chest high-resolution computed tomography (HRCT) scan |
* (1) chest radiograph or, in the absence of cavitation, chest high-resolution computed tomography (HRCT) scan |
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* (3) exclusion of other disorders, such as tuberculosis |
* (3) exclusion of other disorders, such as tuberculosis |
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= Diagnosis = |
== Diagnosis == |
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== Pulmonary disease == |
=== Pulmonary disease === |
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* Diagnosis based on presence of both clinical and microbiological evidence |
* Diagnosis based on presence of both clinical and microbiological evidence |
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** Transbronchial or other lung biopsy with mycobacterial histopathologic features, and either positive culture for NTM or one or more sputum or BALs positive for NTM |
** Transbronchial or other lung biopsy with mycobacterial histopathologic features, and either positive culture for NTM or one or more sputum or BALs positive for NTM |
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== Disseminated disease == |
=== Disseminated disease === |
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* Diagnosis based on MAC in culture of sterile site |
* Diagnosis based on MAC in culture of sterile site |
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= Management = |
== Management == |
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== Pulmonary disease == |
=== Pulmonary disease === |
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* Nodular/bronchiectatic disease: |
* Nodular/bronchiectatic disease: |
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* Refer to Ophthalmology for monitoring while on ethambutol |
* Refer to Ophthalmology for monitoring while on ethambutol |
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== Disseminated disease == |
=== Disseminated disease === |
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* Antibiotics |
* Antibiotics |
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* Duration is until resolution of symptoms and reconstitution of cell-mediated immune function (e.g. CD4 >100) |
* Duration is until resolution of symptoms and reconstitution of cell-mediated immune function (e.g. CD4 >100) |
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== Prophylaxis == |
=== Prophylaxis === |
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* Indicated for adults with (AIDS) with CD4 <50; but not done and no longer in the HIV guidelines |
* Indicated for adults with (AIDS) with CD4 <50; but not done and no longer in the HIV guidelines |
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Revision as of 09:51, 16 August 2019
Microbiology
- A slow-growing non-tuberculous mycobacterium
- Comprises M. avium (subspecies hominissuis in humans) and M. intracellulaire
- 28 serovars between the two
- Can colonize airways and GI tract as well as causing disease
Differential Diagnosis
- Pulmonary disease
- M. kansasii
- M. abscessus
Epidemiology
- Common in the environment, likely acquired by inhalation or ingestion (not person-to-person)
- Water, soil, and animals
- Natural water, indoor water, pools, hot tubs
- Risk factors
- Pulmonary disease: COPD, preior pneumonia, prior TB, steroid use, silicosis, scoliosis, pectus excavatum
- Disseminated disease: HIV, interferon-gamma defects
- Cervical lymphadenitis: children 1-5 years old, HIV with IRIS
Pathophysiology
- In pulmonary disease, likely inhalation ± microaspiration
- In disseminated disease in AIDS, likely GI colonization then replication and dissemination
Clinical Presentation
Pulmonary disease
- Incubation months to years
- Typically presents with non-specific subacute to chronic respiratory syndrome
- Productive cough, weight loss, fevers, night sweats
- CXR often shows upper-lobe infiltrates ± cavitations ± pleural thickening
- Bronchiectasis on CT in 94%
- Mortality is 15% within 2 to 10 years
- Specific populations/presentations:
- Smokers/COPD/alcohol: typical presentation as above
- Lady Windermere syndrome: slower progression
- Hot tub lung disease: a hypersensitivity pneumonitis associated with inhalation
Disseminated disease
- Almost exclusive to HIV patients with CD4 <100
- Median CD4 was 13
- Typically presents with high fevers, weight loss, night sweats, anemia
- Also abdo pain, diarrhea, intraabdo lymphadenopathy, hepatosplenomegaly, and elevated ALP
- Organ-specific involvement: spleen, lymph nodes, liver, adrenals, stomach, CNS
- Often not lung involvement
- Mortality 50% at 4 months
Cervical lymphadenitis
- Disease of children, usually <3 (80% aged 1 to 5 years)
- Presents as painless unilateral lymph node enlargement
- 10% bilateral
Investigations
Pulmonary disease
- (1) chest radiograph or, in the absence of cavitation, chest high-resolution computed tomography (HRCT) scan
- (2) three or more sputum specimens for acid-fast bacilli (AFB) analysis
- (3) exclusion of other disorders, such as tuberculosis
Diagnosis
Pulmonary disease
- Diagnosis based on presence of both clinical and microbiological evidence
- Clinical:
- Pulmonary symptoms, nodular or cavitary opacities on chest radiograph, or an HRCT scan that shows multifocal bronchiectasis with multiple small nodules; and
- Appropriate exclusion of other diagnoses.
- Microbiological:
- Positive cultures from at least two separate expectorated sputum samples; or
- Positive culture from at least one bronchial wash or lavage; or
- Transbronchial or other lung biopsy with mycobacterial histopathologic features, and either positive culture for NTM or one or more sputum or BALs positive for NTM
Disseminated disease
- Diagnosis based on MAC in culture of sterile site
Management
Pulmonary disease
- Nodular/bronchiectatic disease:
- Clarithromycin (1,000 mg) or azithromycin (500 mg)
- Rifampin (600 mg)
- Ethambutol (25 mg/kg)
- Three times weekly (because daily never tolerated)
- If fibrocavitary MAC lung disease or severe nodular/bronchiectatic disease:
- Clarithromycin (500–1,000 mg) or azithromycin (250 mg) daily
- Rifampin (600 mg) or rifabutin (150–300 mg) daily
- Ethambutol (15 mg/kg) daily
- And consider adding three-times-weekly amikacin or streptomycin early in therapy
- Duration is until culture negative on therapy for at least 1 year
- Refer to Ophthalmology for monitoring while on ethambutol
Disseminated disease
- Antibiotics
- Clarithromycin (1,000 mg/d) or azithromycin (250 mg/d)
- Ethambutol (15 mg/kg/d)
- ± rifabutin (150–350 mg/d)
- Duration is until resolution of symptoms and reconstitution of cell-mediated immune function (e.g. CD4 >100)
Prophylaxis
- Indicated for adults with (AIDS) with CD4 <50; but not done and no longer in the HIV guidelines
- Antibiotics: azithromycin 1,200 mg/week or clarithromycin 1,000 mg/day
- Second-line: rifabutin 300 mg/day (less well tolerated)
