Clinical deterioration in community acquired infections associated with lymphocyte upsurge in immunocompetent hosts

Clinical deterioration during the course of community-acquired infections can occur as a result of an exaggerated immune response of the host towards the inciting pathogens, leading to immune-mediated tissue damage. Whether a surge in the peripheral lymphocyte count can be used as a surrogate marker indicating the onset of immunopathological tissue damage is not known. In this study, we report the clinical presentations and outcomes of a cohort of immunocompetent patients with non-tuberculous community acquired infections who experienced clinical deterioration during hospital stay (n=85). 12 (14.1%) patients had a surge in lymphocyte count preceding their clinical deteriorations, and their diagnoses included viral pneumonitis (4), viral encephalitis (3), scrub typhus (2), leptospirosis (1), brucellosis (1), and dengue haemorrhagic fever (1). The clinical manifestations during deterioration ranged from interstitial pneumonitis (6), airway obstruction (1), CNS disturbances (4), and systemic capillary leak syndrome (1), all of which were thought to represent immunopathological tissue damages. When compared with patients without lymphocyte surge, these patients were more likely to be infected with fastidious/viral pathogens (0 vs 12; p<0.05), in addition to having lower mean baseline lymphocyte counts (403±181 vs 1143±686 cells/μl; p<0.05). We postulate that the peripheral lymphocyte count may be a useful surrogate marker indicating the presence of immunopathological damage during clinical deterioration in certain infectious diseases.