Porphyria cutanea tarda (PCT) is the most common form of the porphyria disorders. PCT is caused by a decreased activity of the fifth enzyme in the heme biosynthetic pathway, uroporphyrinogen decarboxylase (UROD; EC 4.1.1.37). In familial PCT (fPCT), the disease is associated with mutations in the gene encoding UROD, but the majority of PCT cases are apparently sporadic (sPCT). Although clinical manifestations are predominated by cutaneous lesions, various degrees of liver damage are often associated with PCT. Clinically manifest PCT usually is provoked by exogenic factors, including alcohol, estrogens, viral hepatitis infections, HIV, and iron (1). A mild to moderate iron overload is common in PCT, and several studies have revealed that the frequency of either of the two known HFE gene mutations associated with hemochromatosis, H63D and C282Y, is substantially higher in PCT patients than in the general population (2)(3)(4)(5)(6)(7)(8). This suggests that the inheritance of these mutations predisposes individuals to development of PCT. Recently, another HFE gene mutation, S65C, was characterized, and analysis of a large group of hemochromatosis probands suggested that S65C may also be associated with hemochromatosis (9)(10). The purpose of the present study was to examine the HFE gene in Danish PCT patients for sequence variations, including the C282Y, H63D, and S65C mutations. Using denaturing gradient gel electrophoresis (DGGE), we screened the entire coding region of the HFE gene in 57 unrelated PCT patients (15 with fPCT and 42 with sPCT). PCT diagnoses were based on the clinical picture and verified by biochemical findings. fPCT and sPCT cases were discriminated by mutation analysis of the …