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What is Hydroa vacciniforme and explain in detail?
Hydroa vacciniforme (HV) is a very rare, chronic photodermatitis-type skin condition with usual onset in childhood. It was first described in 1862 by Bazin. It is sometimes called "Bazins hydroa vacciniforme". A study published in Scotland in 2000 reviewed the cases of 17 patients and estimated a prevalence of 0.34 cases per 100,000 population.  In this study they reported an average age of onset of 7.9 years. Frequently the rash first appeared in the spring or summer months and involved sun-exposed skin.  The rash starts as a vesicular eruption, later becoming umbilicated, and resulted in vacciniform scarring