Glucocorticoid-Associated Leukocytosis (Total White Blood Cell Count)
Systemic glucocorticoids commonly cause an increase in the total white blood cell (WBC) count, largely by producing neutrophilic leukocytosis. [1] The rise in WBC count is attributed primarily to peripheral neutrophil demargination and altered trafficking, with simultaneous decreases in certain lymphocyte subpopulations. [2]
Magnitude and Differential Pattern
Glucocorticoid administration produces neutrophilia with relative increases in circulating neutrophils. [3] Glucocorticoids produce reductions in circulating eosinophils and typically milder reductions in lymphocytes. [3] Monocytes show smaller or less consistent increases than neutrophils in glucocorticoid-associated patterns. [3]
Mechanisms Increasing Total WBC
Glucocorticoids induce neutrophilic leukocytosis through inhibition of neutrophil adhesion to the endothelium and demargination from the marginal pool. [1] Glucocorticoid exposure also reorganizes leukocyte biomechanical and trafficking behavior in vascular microenvironments, supporting increased clinical blood counts. [2] A portion of the leukocyte changes is mediated by effects on lymphoid cell trafficking and glucocorticoid-sensitive cell fate, contributing to lymphopenia. [4]
Mechanisms Reducing Components of WBC
Glucocorticoids cause sequestration and redistribution of lymphocyte populations, which reduces circulating lymphocyte counts. [4] Glucocorticoids can also induce glucocorticoid-sensitive apoptosis in certain activated lymphocyte subsets, contributing to lower circulating lymphocytes. [4]
Timing and Clinical Course
Neutrophil demargination and the associated leukocytosis can occur rapidly after glucocorticoid exposure in humans. [5] The magnitude and duration of WBC changes depend on glucocorticoid dose and exposure characteristics. [5]
Interpretation in the Setting of Infection
Glucocorticoid-associated leukocytosis can occur without infection due to redistribution mechanisms, including demargination of neutrophils. [6] In clinical practice, interpretation of elevated WBC in patients receiving glucocorticoids requires consideration of the glucocorticoid effect and the presence of an alternative infectious or inflammatory cause. [6]
Clinical Implications for Monitoring
With glucocorticoid therapy, peripheral WBC counts may increase in the absence of progressive infection, which can confound diagnostic interpretation of rising leukocyte counts. [6] Persistent or markedly worsening leukocytosis despite appropriate clinical assessment should prompt evaluation for alternative etiologies beyond glucocorticoid demargination. [7]