Genome Editing for Familial Hemophagocytic Lymphohistiocytosis: Design Principles, Challenges, and Translational Perspectives.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome caused by genetic defects in cytotoxic lymphocyte function. Current therapies can control disease activity, but transplantation of allogeneic hematopoietic stem and progenitor cells (HSPCs) remains the only curative option and is associated with substantial risks. These limitations have accelerated development of genome editing approaches enabling precise correction of disease-causing mutations in autologous cells. Familial HLH (FHL) represents a compelling target for genome editing, but successful and safe clinical translation has remained challenging. Preclinical studies demonstrate that targeted editing of key genes, such as PRF1 and UNC13D, can restore cytotoxic function in HSPCs and T cells. Translation to the clinic, however, depends on multiple factors, including the choice of target cell population, the level of functional correction required, and gene-specific constraints such as locus complexity and regulation of gene expression. In this review, we synthesize current progress in genome editing for FHL and highlight critical biological and technical barriers to clinical implementation. We propose a conceptual framework for designing genome editing strategies tailored to FHL, emphasizing the alignment of editing platform, gene architecture, and cellular context to enable effective and clinically translatable therapies.