Which type of solar urticaria is associated with erythropoietic protoporphyria?

The relationship between solar urticaria and erythropoietic protoporphyria is well-established, particularly with Type VI solar urticaria. Erythropoietic protoporphyria is a condition characterized by a deficiency of the enzyme ferrochelatase, leading to an accumulation of protoporphyrin in the skin. When individuals with this condition are exposed to sunlight, they may experience skin reactions, often resembling urticaria.

Type VI solar urticaria specifically refers to a photoallergic reaction that occurs in individuals who have underlying conditions like erythropoietic protoporphyria. The response to sunlight in these patients can result in urticarial lesions due to the unique pathophysiology associated with their condition, which involves phototoxic reactions from accumulated protoporphyrins.

In contrast, the other types of solar urticaria are not linked with erythropoietic protoporphyria. Type I is commonly associated with immunoglobulin E-mediated reactions to sunlight, Type II typically involves a fixed drug eruption or other allergic reactions, and Type III relates to a rare condition that also does not connect with protoporphyrin accumulation. Therefore, recognizing the specific association of Type VI solar