Severe Pertussis During Early Infancy from a High-Altitude Region: Two Clinical Cases and Literature Review

<b>Objective</b>: To investigate how the high-altitude environment modifies severe pertussis in young infants and analyze its pathophysiological mechanisms and clinical management implications. <b>Methods</b>: Clinical data of two young infants with severe pertussis residing at 3650 m were retrospectively analyzed, including presentation, laboratory findings, pathogen detection, treatment, and outcomes. A literature review explored synergistic interactions between high-altitude factors and pertussis pathophysiology. <b>Results</b>: Case 1 had macrolide-resistant <i>Bordetella pertussis</i> (MRBP, 23S rRNA A2047G) with peak WBC 52.25 × 10⁹/L, and received cefoperazone-sulbactam, piperacillin-tazobactam and azithromycin, and was successfully treated with trimethoprim-sulfamethoxazole combined with exchange transfusion. Case 2 had <i>Bordetella pertussis</i> confirmed by PCR with peak WBC 36.55 × 10⁹/L, receiving cefoperazone-sulbactam and azithromycin, and recovered. Both developed respiratory failure requiring non-invasive ventilation and survived without pulmonary hypertension. High-altitude stressors-hypoxia, enhanced pulmonary vascular reactivity, and hypercoagulability-synergize with pertussis-induced hyperleukocytosis as a "dual hit," accelerating cardiopulmonary deterioration and elevating thrombotic risks. <b>Conclusions</b>: High altitude is an independent risk modifier in infantile pertussis, demanding heightened vigilance and proactive interventions: early non-invasive ventilation, prophylactic anticoagulation, and timely exchange transfusion before pulmonary hypertension develops. This is the first high-altitude case series that provides essential insights for clinicians in similar environments globally, guiding early recognition and proactive management strategies to improve outcomes in this vulnerable population.