Objectives: To determine the pathogenic association of latent Epstein-Barr virus (EBV) infections with both typical hydroa vacciniforme (HV) and severe HV-like eruptions, and to survey the complications and outcomes of patients. Design: Case series. Patients: Twenty-nine patients with HV or severe HV-like eruptions. Interventions: In situ hybridization and immunostaining of biopsy specimens; extraction of DNA samples from cutaneous lesions and/or peripheral blood mononuclear cells for EBV DNA assay. Main Outcome Measures: Clinicopathologic manifestations, hematologic findings, complications, and outcomes; presence of latent EBV infection. Results: T cells positive for EBV-encoded small nuclear RNA (EBER) were detected, to various degrees, in cutaneous infiltrates in 28 (97%) of 29 patients, including all 6 patients with definite HV with a positive phototest reaction, 11 of 12 patients with probable HV without evidence of photosensitivity, and all 11 patients with severe HV associated with systemic symptoms. In addition to EBER-positive T cells, many cytotoxic T lymphocytes expressing T-cell intracellular antigen 1 and granzyme B were present in the cutaneous lesions. Natural killer (NK) cells were absent or at a background level. The UV-induced cutaneous lesions showed histopathologic findings consistent with those of HV, containing many EBER-positive cells. Although no hematologic abnormalities were found in the definite and probable HV groups, the amounts of EBV DNA were increased in the peripheral blood mononuclear cells. By contrast, the severe HV group had markedly increased levels of EBV DNA associated with NK-cell lymphocytosis, and complications including chronic active EBV infection, hypersensitivity to mosquito bites, and hemophagocytic syndrome. Five patients with severe disease died of EBV-associated NK/T-cell lymphomas or hemophagocytic syndrome 2 to 14 years after onset. Conclusion: Both typical and severe HV are included within the spectrum of cutaneous disorders mediated by EBV-infected T cells, and the severe HV group may have overt EBV-associated NK/T-cell lymphoproliferative disorders with a frequently fatal outcome.
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