Molecular epidemiology of erythropoietic protoporphyria in the U.K.

BACKGROUND

Erythropoietic protoporphyria (EPP) is a cutaneous porphyria caused by mutations in the ferrochelatase (FECH) or, less frequently, the delta-aminolaevulinate synthase 2 (ALAS2) gene. Predictive genetic counselling requires accurate molecular diagnosis and knowledge of patterns of inheritance.

OBJECTIVES

To investigate the molecular epidemiology of EPP in the U.K.

METHODS

DNA samples from 191 unrelated patients resident in the U.K. were analysed for mutations in the FECH and ALAS2 genes and for the FECH IVS3-48 dimorphism.

RESULTS

Mutations were identified in 179 (94%) patients. Most (169; 94%) had a FECH mutation on one allele and were classified as having pseudodominant EPP (psdEPP); seven (4%) patients had FECH mutations on both alleles (autosomal recessive EPP) and three (2%) patients had ALAS2 mutations (X-linked dominant protoporphyria). The FECH IVS3-48C allele was strongly associated with psdEPP and with the absence of mutations at the FECH or ALAS2 loci. Fifty-six FECH mutations were identified, 19 being previously unreported. Missense mutations were predominant in autosomal recessive EPP (82%) but not in psdEPP (32%). One mutation (c.314 + 2T>G) was present in 41 (24%) of EPP families, most of whom appeared to be descended from a common ancestor resident in the north of England.

CONCLUSIONS

These data define the prevalence and molecular epidemiology of each type of EPP in the U.K.