title: Potential association between calcified thoracic lymphadenopathy due to previous Histoplasma capsulatum infection and pulmonary Mycobacterium avium complex disease.
abstract: BACKGROUND
  Among patients with pulmonary disease due to Mycobacterium avium complex (MAC) seen recently at our center, a substantial number have had extensive calcified mediastinal, hilar, and peribronchial lymphadenopathy, a finding historically inconsistent with pulmonary MAC disease.
  
  
  METHODS
  We retrospectively studied the frequency of calcified lymphadenopathy in the chest and prevalence of known risk factors for MAC infection in 79 patients with pulmonary MAC disease who were referred to our hospital over a 1-year period.
  
  
  RESULTS
  Calcified intrathoracic adenopathy was present in 25 of the 79 patients (32%). Residential histories revealed that 20 of the 25 patients (80%) with such calcified chest adenopathy reported living for substantial periods in the regions indigenous for Histoplasma capsulatum. In contrast, the residences of patients without calcified chest adenopathy were more evenly distributed throughout the country. Nineteen of these 25 patients (76%) with calcified chest adenopathy had no known predisposing risk factor for the infection; in contrast, the proportion of patients with no calcified adenopathy who also had no identifiable classic risk factor tended to be lower (32/54, 59%).
  
  
  CONCLUSIONS
  In this retrospective study, we observed that (1) a large number of patients with pulmonary MAC disease had no identifiable risk factor, (2) calcified chest adenopathy was present in one third of the patients, (3) the residential history of those with calcified adenopathy mirrored the endemic region of histoplasmosis, and, (4) conversely, those patients with pulmonary MAC who lived outside the histoplasmosis belt had no such adenopathy. Thus, we hypothesize that previous fungal infection may predispose the lungs of certain patients to subsequent invasion by MAC, presumably by airway distortion and/or parenchymal damage.
authors.affiliation: Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Health Sciences Center, Denver, CO, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Chan
authors.forename: M D
authors.initials: MD
authors.lastname: Iseman
mesh_terms: D000368:Aged; D002114:Calcinosis / Q000150:complications* / Q000000981:diagnostic imaging; D005260:Female; D006660:Histoplasmosis / Q000150:complications*; D006801:Humans; D008206:Lymphatic Diseases / Q000150:complications* / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D015270:Mycobacterium avium-intracellulare Infection / Q000150:complications*; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D013909:Thorax; D014397:Tuberculosis, Pulmonary / Q000150:complications*