Immune reconstitution is the trigger of herpes zoster with lymphopenia and high neutrophil-to-lymphocyte ratio in a retrospective cohort study.

Background: Herpes zoster (HZ) rarely results in subsequent death, but predictive biomarkers for mortality necessitate further elucidation.

Objectives: To investigate immune dynamics prior to an HZ event, risk factors for HZ onset and immune status at initial HZ.

Methods: This retrospective study extracted from patient records the absolute neutrophil and lymphocyte counts (ANC and ALC, respectively) at the initial HZ date of appearance and up to 30 days before HZ. A follow-up survey was completed within 180 days of onset of illness.

Results: Patients with HZ showed a higher neutrophil-to-lymphocyte ratio (NLR) and lower ALC than patients in the control group at the initial date and had a poorer prognosis. In the pre-onset examination, the maximum and minimum ALC values were significantly lower in patients with HZ than in the control group, and the maximum ALC value in patients with HZ was lower than the minimum value in the control group. The lowest ALC was observed 7 days before the onset of HZ. An NLR of 4.53 or more and an ALC of 0.64 × 109 cells L-1 or less were predictive markers of HZ development within 30 days. Patients who died after HZ had a lower minimum ALC than those who survived longer.

Conclusions: HZ develops in a state of immune reconstitution in patients with immunocompromised conditions, as part of 'unmasking' the immune reconstitution inflammatory syndrome. Lymphopenia prior to HZ onset is one of the most crucial factors in its pathogenesis and vital prognosis. Limitations of the study were small population size, varying age distribution, retrospective nature, and potential overestimation of pre-onset data.