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.