porphyria variegata human 10 Female 8 Male 8 article 8 adult 6 female 6 major clinical study 6 male 6 porphyria cutanea tarda 6 Adolescent 4 Adult 4 Argentina 4 DNA flanking region 4 DNA sequence 4 Erythrocytes 4 Exons 4 Flavoproteins 4 Frameshift Mutation 4 Heme 4 Heterozygote Detection 4 Human 4 Humans 4 Middle Aged 4 Mitochondrial Proteins 4 Mutation, Missense 4 PPOX protein, human 4 Polymerase Chain Reaction 4 Porphyria 4 Porphyria, Variegate 4