Sarcopenia: an overlooked predictor of the progression risk in pulmonary nontuberculous mycobacterial infections?

Background: Pulmonary nontuberculous mycobacterial (pNTM) infection is increasingly diagnosed, particularly in elderly individuals with impaired immunity or comorbidities. While some patients remain stable without treatment, others experience disease progression despite therapy. This study aimed to investigate the association between radiologic progression of pNTM infection and sarcopenia, along with other clinical factors. Methods: This single-center cohort included adults diagnosed with pNTM infection between January 1, 2021, and December 31, 2023, from the institutional picture archiving and communication system and electronic medical records using predefined clinical, radiologic, and microbiologic criteria; 64 patients were included (mean age 66.3±10.71 years). Sarcopenia was evaluated by measuring the cross-sectional area (CSA) of the erector spinae muscles (ESMs) at the T12 level on chest computed tomography (CT), normalized for height to calculate the skeletal muscle index at the level of T12 (T12MI, cm2/m2). Radiologic progression was defined as new or worsening lesions on follow-up CT and was verified through multidisciplinary review. Multivariate logistic regression analyzed associations between T12MI, prior tuberculosis (TB) history, pNTM treatment, and other clinical variables. Results: Ten patients (16%) showed disease progression, including radiologic progression. Sarcopenia (low T12MI) was not significantly associated with progression. In contrast, recent pNTM treatment [odds ratio (OR) =7.167; 95% confidence interval (CI): 1.591–32.291; P=0.01] was significantly associated with progression, and previous TB infection showed a suggestive association (OR =3.500; 95% CI: 0.867–14.133; P=0.08). Conclusions: Sarcopenia was not a significant predictor of radiologic progression in pNTM infection. Instead, treatment history and prior TB were more closely related to progression, suggesting that these clinical factors may be more relevant indicators for radiologic surveillance and management decisions.