Diffuse Large B-cell lymphoma in a Ras-Associated Autoimmune Leukoproliferative Disorder (RALD)

RAS genes are among the most mutated genes in human cancers, with KRAS G12C now being targetable by the specific inhibitor Sotorasib. Ras-associated autoimmune leukoproliferative disorder (RALD) is a rare condition characterized by somatic RAS mutations and hyperactive MAPK signaling. RALD typically affects pediatric patients and is generally considered a benign condition. We report a unique case of RALD in a 76-year-old patient, who is the oldest individual with this disorder to date. This patient also developed lymphoma, marking the fourth known case of malignancy associated with RALD. Additionally, a novel fusion, RHOH::PDCD1LG2 (PD-L2), was identified in the lymphoma, alongside the KRAS mutation. This fusion likely contributes to tumorigenesis through immune evasion.