Clinical characteristics and outcomes of severe Legionella pneumophila pneumonia diagnosed by metagenomic next-generation sequencing in children: a case series of 8 patients.

INTRODUCTION

Severe Legionella pneumophila (LP) pneumonia is exceedingly rare in children, and clinical data remain scarce.

METHODS

We retrospectively analyzed the clinical data of 8 children with severe LP pneumonia diagnosed by metagenomic next-generation sequencing (mNGS) at Henan Children's Hospital between January 2020 and January 2026.

RESULTS

The cohort comprised 3 males and 5 females with a median age of 74 days (range, 8 days to 9 years); neonates accounted for 50.0% (4/8), and 75.0% (6/8) had no underlying diseases. Six cases were community-acquired and 2 were hospital-acquired. The predominant manifestations were tachypnea/dyspnea (100.0%) and fever (87.5%); neonates presented with lethargy and poor feeding. Complications included respiratory failure (87.5%), multiple organ dysfunction (62.5%), and septic shock (37.5%). Procalcitonin, interleukin-6, and LDH were elevated in all cases, while ALB was uniformly decreased. Bilateral pulmonary involvement was seen in 87.5% on chest imaging. mNGS detected LP in all 8 cases (100%), whereas conventional sputum and blood cultures failed to identify LP in any case; LP was isolated from a surgical pus specimen in only 1 case. Co-infections were identified in 50.0%. All initial empirical regimens failed to cover LP. After mNGS-guided targeted therapy, the fluoroquinolone-rifampin combination (2 cases) achieved complete recovery, while macrolide-based regimens yielded variable outcomes. Overall, 50.0% were cured or improved, while 50.0% died or had treatment withdrawn. LP bacteremia and septic shock were uniformly associated with poor outcomes.

DISCUSSION: Severe LP pneumonia in children predominantly affects neonates and can occur without recognized immunodeficiency. mNGS detected LP in all cases where conventional culture failed. In this small cohort, fluoroquinolone-containing combination regimens were associated with favorable outcomes.