A rare skin disorder of unknown etiology affecting children. It is a photodermatitis, characterized by the formation of vesicles and scarring on sun exposed areas.

A vesicular and bullous eruption having a tendency to recur in summer during childhood and commonly appearing on sun-exposed skin. The lesions are surrounded by an erythematous zone and resemble a vaccination. (From Dorland, 27th ed)

In response to the spring sun distinct inflamed reddened skin develops on the ears, nose, cheeks, fingers, backs of the hands, and the lower arms, on which blisters with serous or hemorrhagic content develop. These dry out with the formation of a blackish scab. After shedding of the scab, depressed, varioliform, often hypopigmented scars remain. In addition, hyper- and hypopigmentation are present together, resulting in a polymorphous skin presentation.

Hydroa vacciniforme (HV) is a rare, chronic photodermatosis of unknown origin occurring in childhood. Recurrent vesicles on sun-exposed skin that heal with vacciniform or varioliform scarring characterize HV.