Hydroa vacciniforme

Management Strategy

Onset is generally in childhood between the ages of 5 and 8 years. It is characterized by sun exposure–induced eruptions of vesicular, bullous, and pustular lesions that leave scarring. Lesions develop a few hours after sun exposure, with itchy erythema, progressing over a few days to painful papules and then umbilicated vesicles that crust, and heal with scarring. The cheeks, ears, nose, and dorsum of the hands are the most commonly affected sites. Eye involvement is rare.

Differential diagnosis includes vesicular polymorphic light eruption, actinic prurigo, bullous photosensitive lupus erythematosus, and erythropoietic protoporphyria. However, HV differs from all these conditions, and the clinical diagnosis is usually clear cut.

The photosensitivity and scarring may be severe with a major impact on quality of life.

The rarity of HV explains the lack of large or randomized trials. Recommendations for treatment are based on evidence from case series and single case reports.

Photoprotection is crucial in this disease, which is resistant to specific treatments in most patients. Key measures include restriction of sun exposure, wearing ultraviolet (UV)-protective clothing, regular application of a broad-spectrum sunscreen containing an effective UVA filter, and covering windows in the car and home with films that filter out UV wavelengths below 380 nm.

In patients with the most severe photosensitivity, courses of narrowband UVB (NB-UVB) phototherapy or psoralen with UVA (PUVA) (usually twice weekly for 4–6 weeks as administered for polymorphic light eruption) may help. Phototherapy must be given cautiously to avoid provoking a flare.

More recently antivirals have been considered in view of the causative role of EB virus. A small case series has suggested that this may reduce photosensitivity, but the experience of the authors (HF and RS) is less positive.

Antimicrobial therapy has been tried, as have antimalarials . Systemic immunosuppressants (intermittent oral corticosteroids, azathioprine, and ciclosporin ) have been tried in HV; however, none are reliably effective, and we do not recommend their use since they may be hazardous in chronic active EB virus infection. β-Carotene , used in several studies, has mostly been ineffective.

Dietary fish oil rich in omega-3 polyunsaturated fatty acids was associated with clinical improvement in a small number of patients in four older reports.

All HV is caused by chronic active EBV infection of NK or γδ-T cells. HV is now grouped within the spectrum of diseases known as “HV EBV-associated lymphoproliferative disorders” (HV-LPD).

The higher incidence of HV-LPD in Asia and South America reflects the higher incidence of chronic active EBV infection (CAEBV) of T- and NK-cell types in these populations.

CAEBV infection of NK or γδ-T cells causes a spectrum of severe lymphoproliferative diseases. The only diseases involving the skin are the ‘hypersensitivity to mosquito bites’ syndrome and ‘classic’ and ‘severe’ HV.

‘Severe’ HV has a similar eruption to ‘classic’ HV, but involvement of non-exposed skin, facial edema, and deep ulceration are common, and some patients develop ‘hypersensitivity to mosquito bites’ (necrotic and systemic reactions to insect bites). ‘Severe’ HV is a systemic illness with a bad prognosis, usually requiring treatment with allogeneic bone marrow transplantation.

The major determinant of prognosis is ethnicity. White children from the United States and Europe are unlikely to progress from ‘classic’ HV to ‘severe’ HV. Asian and Hispanic patients are likely to develop the severe disease with systemic involvement.

All patients with HV should be reviewed at least every 6 months for systemic involvement.

HV patients should be managed jointly with an infectious disease or haemato-oncology specialist. If that is not possible, they must be referred to such a specialist if any features are identified, suggesting possible transformation from ‘classic HV’ to a less benign EBV-associated disorder.