While the pathophysiology of SPTCL remains uncertain, biallelic germline coding variants in the hepatitis A virus-cellular receptor 2 (HAVCR2) gene, resulting in decreased expression of the immune checkpoint T-cell immunoglobulin mucin (TIM3), are increasingly implicated in driving the immune dysregulation underlying this disease and are associated with an increased risk of HPS.4 This evidence concerns the gene HAVCR2 and Hermansky-Pudlak syndrome.