INTRODUCTION: Mounier-Kuhn syndrome (MKS) is a rare disorder of the central airways with less than 100 reported cases. We report a patient with MKS infected with multiple nontuberculous mycobacteria.
CASE PRESENTATION: A 48-year-old homeless man with a 15-pack year smoking history and diabetes mellitus presented with the complaint of dyspnea and cough for two weeks. The patient had a history of recurrent pulmonary infections and previous hospitalizations for pneumonia. Chest X-ray revealed right apical bullae with bilateral interstitial changes and bronchiectasis mostly in the upper lung zones. Given his clinical symptoms and his social circumstances, the patient was assessed for active tuberculosis. Induced sputum was positive for acid-fast bacilli and rifampin, isoniazid, pyrazinamide and ethambutol were started. The patient was HIV-negative. Chest CT showed enlarged central airways with a tracheal diameter of 3.6 cm. The right main bronchus measured 2.5 cm and left main bronchus was 2.3 cm. Central and peripheral bronchiectasis, bilateral nodules and bilateral scattered bullae were also noted. Sputum cultures repeatedly grew M. kansasii, M. fortuitum and M. avium intracellulare complex. M. tuberculosis was not cultured and sputum PCR was negative. Azithromycin was replaced with pyrazinamide with the plan to treat until he was culture negative for one year.
DISCUSSIONS: First described in 1932, Mounier-Kuhn syndrome is characterized by enlargement of the trachea and central bronchi with recurrent respiratory tract infections. Pathologically, there is loss or atrophy of the longitudinal elastic fibers and muscularis mucosa in the trachea and bronchi leading to dilatation and increased compliance of the airways. The etiology of MKS is unknown with the majority of cases reported in adulthood. The diagnosis of MKS is made when the diameter of the trachea is greater than 3.0 cm and right and left main stem bronchi are larger than 2.4 and 2.3 cm respectively. Three sub-types are described based on the configuration of the central airways. Our patient fits into the first category typified by symmetrical enlargement of the trachea and main bronchi. Patients with MKS often present with recurrent pulmonary infections. Collapsibility of the airways, especially during expiration, can lead to retained secretions, chronic infections, bronchiectasis and pulmonary fibrosis. We believe that this mechanism explains the etiology of our patient's repeated infections. Nontuberculous mycobacteria are reported with increased frequency in patients with underlying lung disease. It is not surprising that our patient was infected with mycobacteria as patients with COPD and bronchiectasis are often colonized. It is unusual, however, to be infected with multiple mycobacterial species as demonstrated by repeated positive cultures. Patients with these infections often present with symptoms of their underlying disease. To make the diagnosis, the patient needs to have clinical and radiographic findings consistent with mycobacterial lung disease along with two sputum samples, bronchoalveolar lavage or biopsy cultures showing the organism. Our patient had multiple sputum samples that grew M. kansasii, M. fortuitum and M. avium intracellulare with a chest CT showing nodules and bronchiectasis suggesting true infection rather than colonization.
CONCLUSION: MKS should be in the differential in patients with recurrent pulmonary infections. The diagnosis can be made by chest CT. Although nontuberculous mycobacterial infections are often seen in patients with bronchiectasis this is the first reported case in which a patient with MKS was infected with multiple mycobacteria. It is important that patients with MKS be evaluated for these organisms, as it may be an explanation for worsening symptoms.
DISCLOSURE: Santhi Iyer, No Financial Disclosure Information; No Product/Research Disclosure Information