Hemophagocytic Lymphohistiocytosis induced by human granulocytic anaplasmosis: A case report and literature review into the immunopathogenesis

Abstract

Hemophagocytic lymphohistiocytosis (HLH) is a heterogeneous collection of immunological disorders characterized by severely disrupted immune homeostasis and dysregulated macrophage overactivation resulting in hyperinflammation, hypercytokinemia, histiocytic phagocytosis in hematolymphoid systems, and life-threatening organ damage. Human granulocytic anaplasmosis (HGA) is caused by Anaplasma phagocytophilum (Ap), one of the most common tick-borne diseases in North America and worldwide. The pathophysiology by which anaplasmosis triggers the development of human HLH remains unclear. Herein, we report a case of severe Anaplasma infection in Central Pennsylvania presenting with classical clinical features and laboratory findings of acquired, secondary HLH. From basic science to clinicopathological studies, we review and summarize the literature emphasizing the unique immunopathogenesis that informs diagnosis and management of Anaplasma-induced HLH.

Keywords

• Anaplasma
• Hemophagocytic lymphohistiocytosis
• Immunopathogenesis