A patient with elderly-onset atypical hydroa vacciniforme with an indolent clinical course

Hydroa vacciniforme (HV) is a rare photodermatosis that mainly affects children and manifests as vesiculopapular eruptions in sun-exposed areas without systemic symptoms. HV-like lymphoma (HVLL) is one of the Epstein-Barr virus (EBV)-associated lymphoproliferative disorders (LPD) of childhood. Its diagnosis is based on monoclonal T-cell proliferation; however, its degree of malignancy is controversial owing to its variable prognosis. Elderly-onset cases of these diseases are extremely rare, and the clinical features remain unknown. It has been shown that late onset is closely associated with a severe phenotype in EBV-associated LPD including atypical HV. Here we describe a case of elderly-onset atypical HV accompanied by T-cell monoclonality, but with a very indolent clinical course. Our patient indicates a possible case with elderly-onset atypical HV manifesting a favourable course, and that T-cell monoclonality and age of onset cannot always predict the disease severity, and highlights the difficulty of prognosis prediction in elderly-onset atypical HV. What's already known about this topic? Hydroa vacciniforme (HV)-like lymphoma is an Epstein-Barr virus (EBV)-associated disease characterized by T-cell monoclonality, with a rare elderly onset. Late onset is associated with severe phenotype in EBV associated lymphoproliferative disorder. What does this study add? A case of elderly-onset atypical HV with T-cell monoclonality who had a very indolent clinical course is presented. Such a case has never been reported before. Our case demonstrates the possibility of a patient with elderly-onset atypical HV who manifests a favourable course, and that the T-cell monoclonality and age of onset cannot always predict the disease.