BackgroundHaemophagocytic lymphohistiocytosis is a life-threatening disease resulting from primary or secondary hyper-inflammatory disorders. The typical symptoms include persistent fever, splenomegaly, cytopenia and significant elevation of serum ferritin.Case presentationWe report a 30-year-old Chinese female patient who was diagnosed with chronic active Epstein-Barr virus infection more than 9months prior and has since been presenting with cutaneous lymphoproliferative disorders mimicking hydroa vacciniforme and subsequent haemophagocytic lymphohistiocytosis. Exome sequencing suggested novel digenic heterozygous STXBP2 (c.592A>C, p.Thr198Pro) and LYST (c.830A>T, p.His277Leu) mutations.ConclusionsThis is the first case report in which adult HLH was associated with novel digenic mutations of STXBP2 and LYST combined with Epstein-Barr virus infection. It could also be the first polygenic model report, given that the pathogenicity of other mutated genes still remains unclear. We additionally conducted an in-depth, two-generation pedigree analysis to further illustrate the mode of inheritance in this case.