EPP and XLP are both protoporphyrias with similar symptoms and similar biochemical findings, but each is caused by mutations in a different gene. EPP is a deficiency of the enzyme, ferrochelatase, due to mutations in FECH gene. The inheritance of EPP follows an autosomal recessive pattern: most cases due to a severe mutation on one FECH allele (inherited from one parent), and a specific common genetic variation on the other FECH allele (inherited from the other parent). This common genetic variation causes reduced production of the enzyme, but does not cause disease in the absence of a severe mutation. Alternatively, some EPP cases result from two severe FECH gene mutations, one inherited from each parent.
Symptoms usually first occur in early childhood, and include sun sensitivity, marked by severe pain and swelling of sun-exposed areas, but typically with no blistering or scarring. Both EPP and XLP result in significant elevations of protoporphyrins in the liver, sometimes resulting in severe liver complications that are difficult to treat and sometimes require liver transplantation. DNA analysis of the FECH gene is performed by full gene sequencing of all exons (coding regions), 20-30 base pairs into the introns (including splice sites), and the promoter region. This methodology should identify >98% of mutations listed in the Human Gene Mutation Database as well as novel mutations.
Specimen Requirements: Two 10 mL EDTA (lavendar top) tubes and one 10 mL ACD (yellow top) tube. Two to three confluent T-25 flasks of cultured cells and one control flask are required for prenatal samples.
Shipping: Send at room temperature.
Turnaround Time: 14 days
CPT Codes: 83891, 83898x11, 83904x5, 83912
Consent Form: Porphyria Genetic Testing Consent [PDF]
Requisition Form: Porphyria Testing Requisition [PDF]
Prior to ordering prenatal testing, please contact our laboratory at 212-241-7518 to discuss.