Hydroa vacciniforme: a chronic photodermatitis
The Hydroa vacciniforme is a type of photodermatitis which is not frequent and which is characterized by an intermittent cicatricial and bullous eruption which is induced by exposition of skin to sunlight. This condition generally affects men than women in a relation of 2:1 and begins to appear on the first decade of life, it means during childhood. The causative agent for the Hydroa vacciniforme is unknown, although according to the clinic of acute attacks and symmetrical lesions which emerge only on exposed areas of skin, this condition can correspond to a variant of solar polymorphic eruption.
Primary lesions consist of edematous and pruritic macules or wheals which emerge on skin before twenty four hours have passed after the exposition of skin to sunlight. They are symmetrically placed on the nose, cheeks, neck, ear, dorsal surface of hands and extensor surface of extremities. These lesions progress to vesicles and confluent bullae, they can be sometimes hemorrhagic and with an erythematous base. In three or four days is produced a central dimpling and adherent crust varioliform of a brownish color.
There can be observed recurrence after exposition of skin to sunlight. It is frequent the spontaneous resolution of the condition during adolescence. This condition is characterized for being chronic, and after the lesions produced by this condition remit, they leave varioliform scars. The Hydroa vacciniforme is an entity with clinical and histological characteristics that are very specific and which are useful to develop the diagnosis of the condition. The prevalence of this entity is sporadic although there have been reported cases of entire families affected and even of fraternal twins affected by it.
The clinical manifestations are characterized by the presence of vesico-bullous erythematous lesions in areas that are photo exposed which leave varioliform scars. In patients affected by this condition is very frequent the great ocular compromise given by a walleye, conjunctival congestion, corneal keratopatía, photophobia and cicatricial ectropion which is affecting in a severe way to one of the eyes of the patient. Besides the deforming scars on face there can be observed scars on ears and contractures with functional impotence on fingers.
The differential diagnosis of this condition includes the solar polymorphic eruption, bullous lupus erythematosus, erythropoietic protoporphyria and actinic prurigo which can be discarded considering the anamnesis of the patient, physical findings like scars, a histological exam and lab exams. There should be considered too in the differential diagnosis to the patients which present clinical manifestation similar to lymphoma and an infection for EBV which are considered as atypical hydroa vacciniforme reported in Asia and in Latin America; which has a specific histopathology that consists in an atypical lymphocytic infiltrate in the dermis. The etiology of the condition is still unknown; there is theory of an abnormal sensitivity to the UVA (Ultraviolet rays type A) radiation in a range of 320 to 390 nm of wavelength. The chromophore which would cause this damage induced by ultraviolet radiation on the HV is unknown.