Case 88 (3 July 1999)


Diagnosis: Mycobacterial Infection Other Than Tuberculosis
(M. avium-intracellulare)

Radiologic Findings

  • Chest radiograph shows bronchial dilatation with wall thickening and multiple irregular marginated nodules in both lungs.
  • Conventional & HRCT revealed centrilobular nodules, branching linear structures, tree-in-bud and conglomeration of nodules,suggestive of bronchogenic spread of the disease and pleomorphism.
  • Multifocal bronchiectatic changes are noted in RML, left lingular division, and both lower lobes without correlation with above-mentioned nodules.   
     



 

Brief Review

  • A number of mycobacteria other than M. tuberculosis (MOTT) have been identified as cases of pulmonary infection. These include M. kansasii, M. avium-intracellulare, M. fortuitum, M. xenopi, M. chelonae, and M. simiae.
     
  • It appears that M. avium-intracellulare and M. kansasii are the most common pathogens in immunocompromised hosts. The incidence of MOTT in the non-HIV-infected population is approximately 2/100,000 population, probably remained fairly stable because infection occurs from the natural environment and not by person-to-person transmission.
     
  • The organisms have a prediction for individuals with preexisting chronic obstructive pulmonary disease or with debilitating illnesses or various forms of immunocompromise. An interesting association has been observed with achalasia of gastric cardia and M. fortuitum / chelonae infection. Presumably these organisms flourish in the dilated obstructed esophagus and heavily seed the lungs during episodes of aspiration. One of the problems in the study of the clinical and radiologic manifestations of MOTT infection has been that these organisms may occurs as incidental contaminants.
  • The classic features of MOTT infections of the lung are those of chronic indolent fibrocavitary processes. In many instances, the radiographic features are indistinguishable from those of reactivation of M. tuberculosis. The response to antituberculous therapy may be poor, and a seemingly inexorable progression of the disease over a period of years is common.
     
  • The most common radiographic abnormality was multiple pulmonary nodules, suggestive bronchogenic spread pattern. Bronchiectasis was higher than M. tuberculosis, found in mainly RML, BLL, and lingular division. Cavitation was revealed at some stage of the disease. Other findings included granuloma, parenchymal scarring, mediastinal lymphadenopathy and consolidations. Progression of disease and response to treatment were slow except M. chelonae.

 


 

References
  1. Contreras MA, Cheung OT, Sanders DE, et al : Pulmonary infection with nontuberculous Mycobacteria, Am Rev Respir Dis 1988; 137: 149-152
     
  2. Aronchick JM, Miller WT, Epstein DM, et al : Association of achalasia and pulmonary
    Mycobacterium Fortuitum infection, Radiology 1986; 160: 85-86
     
  3. Davidson PT : The diagnosis and management of disease caused by M. avium complex,M. kansassi and other mycobacteria, Clin Chest Med 1989; 10: 431-443
     
  4. Albelda SM, Kern JA, Marinelli DL, et al : Expanding spectrum of pulmonary disease
    caused by nontuberculous mycobacteria, Radiology 1985; 157: 289-296
     
  5. Prince DS, Peterson DD, Steiner RM, et al : Infection with Mycobacterium avium complex in patients without predisposing conditions, N Engl J Med 1989; 321: 863-868  



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