We describe a case of a 6-year old male initially diagnosed with solar urticaria but found to have a genetically based disorder of heme synthesis.

The patient presented with a 3-year history of a photosensative dermatosis which occurred during each summer season. He routinely developed pruritic, erythematous, and indurated skin eruptions to the face and arms within minutes of sun exposure. The lesions were not responsive to anti-histamine therapy and would remit within 48 hours. Past medical history was only significant for allergic rhinitis. Family history was significant for a similar rash to sun exposed areas in the mother and allergic rhinitis in the father.

On exam there was evidence of dermal xerosis, hyperpigmentation and cicatrix formation over the face and hands. No significant lymphadenopathy or hepato-splenomegaly. Laboratory evaluation revealed a mild normochromic normocytic anemia (Hgb=11.2 g/dL), normal ESR and urinalysis, elevated total bilirubin (1.7 mg/dL), and a highly elevated erythrocyte protoporphyrin (>350 ug/dL). An autoimmune screen and 24- hour urine for porphyrin, porphobilinogen and delta-aminolevulinic acid were all negative.

Erythropoetic Protoporphyria was diagnosed in view of the clinical history and strong laboratory evidence. He had an excellent clinical response to treatment with oral beta-carotene, daily sunscreen, and topical zinc oxide. In summary, this is a young atopic male with porphyria who was originally diagnosed as having sun induced urticaria. As solar urticaria is a rare disorder, especially in children, suspected cases should be carefully assessed to rule out a rheumatologic or metabolic cause for their condition.