Exacerbation of erythropoietic protoporphyria by hyperthyroidism.

Erythropoietic protoporphyria (EPP) is a hereditary disorder caused by deficiency of ferrochelatase, the last enzyme in the heme biosynthetic pathway. The majority of EPP patients present with a clinical symptom of painful phototoxicity. Liver damage, the most serious complication of EPP, occurs in <5% of the patients. This report describes a case of an EPP patient who complained of worsening cutaneous symptoms, nervousness, and insomnia. Laboratory tests showed highly increased protoporphyrin concentration in erythrocytes and elevated serum transaminases that are indicative of EPP-related liver damage. The subsequent finding of decreased serum thyroid-stimulating hormone (TSH) and increased free triiodothyronine (FT3) and free thyroxine (FT4) concentrations, as well antibodies against both thyroid peroxidase (TPO) and TSH receptors, led to the diagnosis of Graves' disease. The patient received 500 MBq of radioiodine (I(131)). Three months after the radioactive iodine therapy, the thyroid volume was reduced to 30% of pretherapeutic volume. Although the patient was slightly hypothyroidic, his liver enzymes returned to normal, his erythrocytic protoporphyrin concentration dropped fivefold, and his skin symptoms improved dramatically. The coexistence of Graves' disease and EPP is a statistically rare event as, besides our patient, there was one additional case reported in the literature. Although the exact mechanism whereby Graves' disease interacts with EPP is yet to be explored, we recommend testing thyroid function in EPP patients with liver complication to exclude hyperthyroidism as a potential cause.