After antiviral and antifungal treatments, EBV-DNA levels normalized, cerebrospinal fluid examination returned to normal, and primary HLH with an UNC13D gene mutation was confirmed by gene sequencing.<h4>Conclusions</h4>While primary HLH is more prevalent in infants and young children, it can also occur in adolescents and adults, often being misdiagnosed as secondary HLH due to concurrent EBV infection. Here, UNC13D is linked to Epstein-Barr virus infection.