Mediastinal lymphadenitis caused by Mycobacterium avium complex in children: a rare case of airway compression.

UNLABELLED: Airway compression caused by intrathoracic non-tuberculous mycobacteria (NTM) lymphadenitis is particularly uncommon in otherwise healthy children and remains poorly characterized. We aimed to describe the clinical, radiological, microbiological, and immunological features of a French pediatric cohort diagnosed with mediastinal Mycobacterium avium complex (MAC) lymphadenitis. We conducted a retrospective multicenter study that included children diagnosed with bacteriologically confirmed intrathoracic MAC lymphadenitis in France between 2009 and 2024. Patients with HIV-related immunodeficiency or known inborn errors of immunity were excluded. Immunological investigations were performed, including the secretion of IL-12 and IFN-γ by a whole-blood assay. Ten children with intrathoracic MAC lymphadenitis with airway compression were included. In most cases, the diagnosis required invasive sampling. Mycobacterium avium was identified in nine patients and M. intracellulare in one patient. Main respiratory manifestations were dyspnea, persistent cough, and abnormal breath sounds. Chest computed tomography (CT) scans revealed mediastinal lymphadenopathies causing airway compression, ventilation disorders, and air trapping. Following prolonged antibiotic treatment, all patients showed clinical improvement and a reduction in lymph node size, although residual calcifications frequently persisted. IFN-γ secretion was impaired in all five patients who underwent specific immunological testing, consistently lower compared with healthy controls.

CONCLUSION: This study highlights a rare presentation of airway compression in children characterized by MAC mediastinal lymphadenitis. These findings underscore the importance of considering NTM infections in the differential diagnosis of persistent mediastinal lymphadenitis in young children and highlight the frequent need for invasive sampling to establish a microbiological diagnosis. Although no overt immunodeficiency was identified, immune evaluation, particularly exploration of the IFN-γ-mediated immunity, may be relevant in these patients.

WHAT IS KNOWN: • Mediastinal lymphadenitis caused by non-tuberculous mycobacteria (NTM) is a rare condition, mainly reported in immunocompromised patients, and often mimics tuberculosis on imaging. • Diagnosis is challenging due to nonspecific clinical and radiological findings, and it relies on microbiological confirmation.

WHAT IS NEW: • In this cohort, intrathoracic MAC infection in young children presented as airway-compressive mediastinal lymphadenitis rather than classical parenchymal pulmonary NTM disease. • Bronchoalveolar lavage had a low diagnostic yield, and most cases required targeted lymph node or endobronchial granuloma sampling. • A subset of tested patients showed reduced IFN-γ secretion despite the absence of a known monogenic immunodeficiency.