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Pulmonary Mycobacterium avium Complex (MAC) Infection


General Information


  • pulmonary disease due to a species within MAC1,2
    • species in the complex include Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium chimaera (latter recently added)
    • slow-growing nontuberculous mycobacteria
    • the clinical syndromes associated with each are clinically indistinguishable
  • major pulmonary manifestations of MAC include1
    • apical fibrocavitary lung disease
    • nodular lung disease with bronchiectasis
  • MAC species are also associated with "hot tub lung disease," a hypersensitivity reaction in the lung in response to colonization or infection1
  • dissemination of MAC is rare with pulmonary disease1

Also called

  • MAC infection
  • Mycobacterium avium-intracellulare infection
  • MAI infection
  • Lady Windermere syndrome
  • hot tub lung (used for hypersensitivity pneumonitis associated with MAC)


  • Nontuberculous Mycobacteria Network - Network European Trials Group (NTM-NET) treatment outcome definitions for nontuberculous mycobacterial pulmonary disease
    Culture conversion≥ 3 consecutive negative mycobacterial cultures from respiratory samples collected ≥ 4 weeks apart during treatment
    Microbiologic cureMultiple consecutive negative and no positive cultures with the causative species from respiratory samples after culture conversion through the end of treatment
    Clinical cureIn the absence of evidence of culture conversion or microbiologic cure, patient-reported and/or objective improvement in symptoms on treatment that is sustained through end of treatment
    CureTreatment completion with both microbiologic and clinical cure
    Treatment failureRe-emergence of ≥ 2 positive cultures or persistence of positive cultures with causative species from respiratory samples after ≥ 12 months of treatment while still on treatment
    RecurrenceRe-emergence of ≥ 2 positive cultures with causative species from respiratory samples after ending treatment; may be relapse or reinfection
    RelapseEmergence of ≥ 2 positive cultures with same causative strain after treatment
    ReinfectionEmergence of ≥ 2 positive cultures with a different causative strain after treatment


  • 2 major pulmonary manifestations1,2,4
    • apical fibrocavitary lung disease
      • usually involves upper lobe
      • severe and progressive form of disease (can result in extensive cavitary lung destruction and respiratory failure in 1-2 years)
      • typically develops in patients (more often men aged 40-50 years) with underlying pulmonary disease and/or history of smoking
    • nodular lung disease with bronchiectasis (often referred to as Lady Windermere syndrome in older women)
      • usually involves mid and lower lung
      • bronchiectasis may be previously existing and exacerbated by infection or develop de novo
      • ranges from indolent chronic condition to severe disease
      • typically develops in postmenopausal, nonsmoking women with low body mass index or skeletal deformities such as scoliosis, pectus excavatum, mitral valve prolapse (MVP), or joint hypermobility
  • hypersensitivity lung disease ("hot tub lung disease")1,2
    • also associated with MAC
    • etiology not fully elucidated but likely a combination of infection and aberrant inflammatory response


General references used

  1. Griffith DE, Aksamit T, Brown-Elliott BA, et al; American Thoracic Society/Infectious Disease Society of America (ATS/IDSA). An official ATS/IDSA statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases. Am J Respir Crit Care Med. 2007 Feb 15;175(4):367-416OpenInNew, correction can be found in Am J Respir Crit Care Med 2007 Apr 1;175(7):744, commentary can be found in Am J Respir Crit Care Med 2007 Aug 15;176(4):418OpenInNew
  2. Kasperbauer SH, Daley CL. Diagnosis and treatment of infections due to Mycobacterium avium complex. Semin Respir Crit Care Med. 2008 Oct;29(5):569-76OpenInNew
  3. Prevots DR, Marras TK. Epidemiology of human pulmonary infection with nontuberculous mycobacteria: a review. Clin Chest Med. 2015 Mar;36(1):13-34OpenInNewfull-textOpenInNew
  4. Philley JV, Griffith DE. Treatment of slowly growing mycobacteria. Clin Chest Med. 2015 Mar;36(1):79-90OpenInNew
  5. Egelund EF, Fennelly KP, Peloquin CA. Medications and monitoring in nontuberculous mycobacteria infections. Clin Chest Med. 2015 Mar;36(1):55-66OpenInNew

Recommendation grading systems used

  • American Thoracic Society/Infectious Disease Society of America (ATS/IDSA) rating system adapted from Infectious Disease Society/United States Public Health Service rating system
    • strength of recommendation
      • Grade A - good evidence to support recommendation for use
      • Grade B - moderate evidence to support recommendation for use
      • Grade C - poor evidence to support recommendation for or against use
      • Grade D - moderate evidence to support recommendation against use
      • Grade E - good evidence to support recommendation against use
    • quality of evidence
      • Level I - evidence from at least 1 properly randomized, controlled trial
      • Level II - evidence from at least 1 well-designed clinical trial without randomization, from cohort or case-controlled analytic studies (preferably from more than 1 center), from multiple time-series studies or from dramatic results in uncontrolled experiments
      • Level III - evidence from opinion of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees
    • Reference - ATS/IDSA guideline on diagnosis, treatment, and prevention of nontuberculous lung disease (17277290Am J Respir Crit Care Med. 2007 Feb 15;175(4):367OpenInNew)

Synthesized Recommendation Grading System for DynaMed

  • DynaMed systematically monitors clinical evidence to continuously provide a synthesis of the most valid relevant evidence to support clinical decision-making (see 7-Step Evidence-Based MethodologyOpenInNew).
  • Guideline recommendations summarized in the body of a DynaMed topic are provided with the recommendation grading system used in the original guideline(s), and allow DynaMed users to quickly see where guidelines agree and where guidelines differ from each other and from the current evidence.
  • In DynaMed (DM), we synthesize the current evidence, current guidelines from leading authorities, and clinical expertise to provide recommendations to support clinical decision-making in the Overview & Recommendations section.
  • We use the Grading of Recommendations Assessment, Development and Evaluation (GRADE)OpenInNew to classify synthesized recommendations as Strong or Weak.
    • Strong recommendations are used when, based on the available evidence, clinicians (without conflicts of interest) consistently have a high degree of confidence that the desirable consequences (health benefits, decreased costs and burdens) outweigh the undesirable consequences (harms, costs, burdens).
    • Weak recommendations are used when, based on the available evidence, clinicians believe that desirable and undesirable consequences are finely balanced, or appreciable uncertainty exists about the magnitude of expected consequences (benefits and harms). Weak recommendations are used when clinicians disagree in judgments of relative benefit and harm, or have limited confidence in their judgments. Weak recommendations are also used when the range of patient values and preferences suggests that informed patients are likely to make different choices.
  • DynaMed (DM) synthesized recommendations (in the Overview & Recommendations section) are determined with a systematic methodology:
    • Recommendations are initially drafted by clinical editors (including ≥ 1 with methodological expertise and ≥ 1 with content domain expertise) aware of the best current evidence for benefits and harms, and the recommendations from guidelines.
    • Recommendations are phrased to match the strength of recommendation. Strong recommendations use "should do" phrasing, or phrasing implying an expectation to perform the recommended action for most patients. Weak recommendations use "consider" or "suggested" phrasing.
    • Recommendations are explicitly labeled as Strong recommendations or Weak recommendations when a qualified group has explicitly deliberated on making such a recommendation. Group deliberation may occur during guideline development. When group deliberation occurs through DynaMed-initiated groups:
      • Clinical questions will be formulated using the PICO (Population, Intervention, Comparison, Outcome) framework for all outcomes of interest specific to the recommendation to be developed.
      • Systematic searches will be conducted for any clinical questions where systematic searches were not already completed through DynaMed content development.
      • Evidence will be summarized for recommendation panel review including for each outcome, the relative importance of the outcome, the estimated effects comparing intervention and comparison, the sample size, and the overall quality rating for the body of evidence.
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      • All recommendation panel members must disclose any potential conflicts of interest (professional, intellectual, and financial), and will not be included for the specific panel if a significant conflict exists for the recommendation in question.
      • Panel members will make Strong recommendations if and only if there is consistent agreement in a high confidence in the likelihood that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. Panel members will make Weak recommendations if there is limited confidence (or inconsistent assessment or dissenting opinions) that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. No recommendation will be made if there is insufficient confidence to make a recommendation.
      • All steps in this process (including evidence summaries which were shared with the panel, and identification of panel members) will be transparent and accessible in support of the recommendation.
    • Recommendations are verified by ≥ 1 editor with methodological expertise, not involved in recommendation drafting or development, with explicit confirmation that Strong recommendations are adequately supported.
    • Recommendations are published only after consensus is established with agreement in phrasing and strength of recommendation by all editors.
    • If consensus cannot be reached then the recommendation can be published with a notation of "dissenting commentary" and the dissenting commentary is included in the topic details.
    • If recommendations are questioned during peer review or post publication by a qualified individual, or reevaluation is warranted based on new information detected through systematic literature surveillance, the recommendation is subject to additional internal review.

DynaMed Editorial Process

Special acknowledgements

  • DynaMed topics are written and edited through the collaborative efforts of the above individuals. Deputy Editors, Section Editors, and Topic Editors are active in clinical or academic medical practice. Recommendations Editors are actively involved in development and/or evaluation of guidelines.
  • Editorial Team role definitions
    Topic Editors define the scope and focus of each topic by formulating a set of clinical questions and suggesting important guidelines, clinical trials, and other data to be addressed within each topic. Topic Editors also serve as consultants for the internal DynaMed Editorial Team during the writing and editing process, and review the final topic drafts prior to publication.
    Section Editors have similar responsibilities to Topic Editors but have a broader role that includes the review of multiple topics, oversight of Topic Editors, and systematic surveillance of the medical literature.
    Recommendations Editors provide explicit review of DynaMed Overview and Recommendations sections to ensure that all recommendations are sound, supported, and evidence-based. This process is described in "Synthesized Recommendation Grading."
    Deputy Editors are employees of DynaMed and oversee DynaMed internal publishing groups. Each is responsible for all content published within that group, including supervising topic development at all stages of the writing and editing process, final review of all topics prior to publication, and direction of an internal team.

How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T906532, Pulmonary Mycobacterium avium Complex (MAC) Infection; [updated 2018 Nov 30, cited place cited date here]. Available from Registration and login required.
  • KeyboardArrowRight

    Overview and Recommendations

    • Background

    • Evaluation

    • Management

  • Related Summaries

  • KeyboardArrowRight

    General Information

    • Description

    • Also called

    • Definitions

    • Types

  • KeyboardArrowRight


    • Geographic distribution

    • KeyboardArrowRight


      • Pulmonary nontuberculous mycobacterial (NTM) prevalence worldwide

      • Pulmonary NTM prevalence in United States

    • KeyboardArrowRight

      Risk factors

      • Risk factors for acquisition

      • Risk factors for disease subtypes

      • Risk factors for disseminated disease

    • KeyboardArrowRight

      Associated conditions

      • Hypersensitivity-like lung disease

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    Etiology and Pathogenesis

    • Pathogen

    • Transmission

    • Pathogenesis

    • Immune response

  • KeyboardArrowRight

    History and Physical

    • KeyboardArrowRight


      • Chief concern (CC)

      • Medication history

      • Past medical history (PMH)

      • Social history (SH)

    • KeyboardArrowRight


      • General physical

      • Cardiac

      • Lungs

      • Musculoskeletal

  • KeyboardArrowRight


    • Making the diagnosis

    • Differential diagnosis

    • Testing overview

    • Blood tests

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      Imaging studies

      • Chest x-ray

      • High-resolution computed tomography (HRCT)

    • KeyboardArrowRight

      Microbiologic testing

      • Specimen collection

      • Smear for acid-fast bacillus (AFB)

      • Culture

      • Antimicrobial susceptibility testing

  • KeyboardArrowRight


    • Management overview

    • KeyboardArrowRight


      • Recommendations

      • KeyboardArrowRight

        First-line antimicrobials

        • Efficacy

        • Dosing

        • Adverse effects

      • KeyboardArrowRight

        Barriers to treatment success

        • Antimicrobial resistance

        • Low protocol adherence

      • Salvage antimicrobial regimens

    • Surgery and procedures

    • Follow-up

  • KeyboardArrowRight

    Complications and Prognosis

    • Complications

    • KeyboardArrowRight


      • Response to treatment

      • Mortality

      • Relapse or reinfection

  • KeyboardArrowRight

    Prevention and Screening

    • Prevention

  • KeyboardArrowRight

    Guidelines and Resources

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      • United States guidelines

      • United Kingdom guidelines

      • Asian guidelines

    • Review articles

    • MEDLINE search

  • Patient Information

  • KeyboardArrowRight

    ICD Codes

    • ICD-10 codes

  • KeyboardArrowRight


    • General references used

    • Recommendation grading systems used

    • Synthesized Recommendation Grading System for DynaMed

    • DynaMed Editorial Process

    • Special acknowledgements

    • How to cite

Topic Editor
Renee Ridzon MD

Adjunct Associate Professor, Boston University School of Public Health; Massachusetts, United States

Conflicts of Interest

Dr. Ridzon declares no relevant financial conflicts of interest.

Recommendations Editor
Zbys Fedorowicz MSc, DPH, BDS, LDSRCS

Director of Bahrain Branch of the United Kingdom Cochrane Center, The Cochrane Collaboration; Awali, Bahrain

Conflicts of Interest

Dr. Fedorowicz declares no relevant financial conflicts of interest.

Deputy Editor
Alan Ehrlich MD, FAAFP

Executive Editor, DynaMed; Associate Professor of Family Medicine, University of Massachusetts Medical School; Massachusetts, United States

Conflicts of Interest

Dr. Ehrlich declares no relevant financial conflicts of interest.

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