Background: Erythropoietic protoporphyria (EPP) is known to be inherited in both autosomal dominant and recessive manners. A deleterious mutation in conjunction with a polymorphic wild type allele underlies the molecular basis of the dominant type.
Methods: We report a patient with EPP who was found to have a novel large deletion [c.1-9628_67+2871del12566 bp] and three polymorphisms [c.1-251A>G, c.68-23C>T and c.315-48T>C] in trans to the deletion in his ferrochelatase (FECH) gene.
Results: The combination of the deletion and the polymorphisms reduced his FECH activity level to 20% of control.
Conclusions: It is conceivable that a homozygous state for this polymorphic haplotype might be sufficient to produce clinical phenotype of EPP. The boundary between autosomal dominant and autosomal recessive inheritance may not always be distinct.