Patterns of Disease in Patients with Middle-Lobe Predominant Bronchiectasis.

Background: Middle-lobe predominant bronchiectasis affecting the right middle-lobe and/or lingula (RMLP) is classically described in asthenic, elderly females with skeletal abnormalities or associated nontuberculous mycobacterial (NTM) infection.

Objectives: We aimed to evaluate the frequency and clinical characteristics of patients with an RMLP phenotype in a cohort of newly diagnosed bronchiectasis patients and determine associations with disease severity.

Methods: A retrospective observational cross-sectional cohort study of consecutive bronchiectasis patients in our institution was performed. Data were collected on baseline variables, microbiology status, lung function, and radiology according to the modified Bhalla score. Disease severity was assessed using bronchiectasis severity index (BSI) and FACED severity scores.

Results: Of 81 patients (mean age [SD] 62.6 [12.4], females 55 [67.9%], BMI 26.9 [5.7%]), 20 (24.7%) had RMLP disease. These patients were significantly younger, female, and with lower BMIs than patients with the classical bronchiectasis phenotype (p = 0.03, 0.01, and p <0.01, respectively). Fewer symptoms of cough and daily sputum (p = 0.01 and <0.01), prior exacerbation frequency (p = 0.03), and higher baseline forced expiratory volume (p = 0.04) were noted. A higher incidence of NTM at diagnosis was demonstrated (p = 0.01). BSI and FACED severity scores in RMLP patients were significantly lower than their counterparts (both p < 0.001).

Conclusions: The RMLP phenotype is associated with younger patients than classically described in the literature. An increased rate of NTM infection in this phenotype was noted, particularly in females, but much lower than previously described. Lung function and disease severity scores in this patient group are relatively normal, suggesting a milder phenotype in patients with this form of the disease.