Case Report: A case of severe mosquito bite allergy in an elderly patient

Background: Severe mosquito bite allergy (SMBA) is characterized by intense local necrotic skin reactions accompanied by systemic symptoms following mosquito bites. SMBA is currently classified within the spectrum of EBV-positive T/natural killer (NK)-cell lymphoproliferative disorders (LPDs) and is recognized as a specific cutaneous manifestation of chronic active EBV disease (CAEBVD), with a potential risk of progression to overt T/NK-cell leukemia or lymphoma. Case presentation: Herein, we report a rare case of a 70-year-old male diagnosed with EBV-associated NK-cell LPD manifesting primarily as SMBA. The patient presented with recurrent disseminated erythematous plaques, bullae, necrotic ulcers, and scarring following mosquito bites, accompanied by intermittent fever. Quantitative PCR revealed a high EBV DNA load in peripheral blood, and skin biopsy demonstrated an angiocentric infiltration of EBV-positive NK cells. Based on the clinical features of SMBA, high EBV load, and histopathological findings, the diagnosis of EBV-associated NK-cell LPD was established. Treatment with oral prednisone and methotrexate resulted in significant clinical improvement, and the patient maintained a stable, indolent course during the subsequent 2-year follow-up. Conclusion: We report a rare case of elderly-onset EBV-associated NK-cell LPD manifesting as SMBA, characterized by an unusually indolent clinical course. Furthermore, we provide a comprehensive literature review of 9 previously reported adult SMBA cases to offer insights for clinical practice.