Acute Porphyrias Panel
Related Gene(s): CPOX, HMBS, PPOX
Three of the porphyrias – acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP) – are associated with acute attacks and have similar symptoms. They may be grouped together as “acute hepatic porphyrias.”
AIP, HCP, and VP are each caused by a specific enzyme deficiency in the heme biosynthesis pathway (hydroxymethylbilane synthase, coproporphyrinogen oxidase, and protoporphyrinogen oxidase, respectively), due to a mutation in specific genes (HMBS, CPOX, or PPOX, respectively). All three diseases are autosomal dominant traits. The enzyme deficiency alone is not sufficient to produce the symptoms of AIP, HCP, or VP. Other activating factors, such as drugs, hormones, and dietary changes must be present. Sometimes activating factors cannot be identified.
Most people who have a mutation in the gene for AIP, HCP, or VP never develop symptoms. This is referred to as “latent” AIP, HCP, or VP. Symptoms may develop after puberty, especially in women. Unlike AIP, symptoms of HCP and VP may also include photosensitivity.
Acute attacks are typically characterized by severe abdominal pain. However, sometimes the pain may begin in the chest, back, or thighs. Patients also experience nausea, vomiting, constipation, and increased heart rate and blood pressure. These symptoms and signs are all due to the effects of the disease on the nervous system. Confusion, convulsions, and muscular weakness, due to neurologic impairment, may lead to paralysis. An acute attack usually lasts for days or longer. Recovery from severe paralysis is generally slow.
DNA analysis of the HMBS, CPOX, and PPOX genes is performed as a panel by full gene sequencing of all exons (coding regions), 20-30 base pairs into the introns (including splice sites), and the promoter region of each of the respective genes. This methodology should identify >98% of gene mutations reported in the Human Gene Mutation Database, as well as novel mutations.
- For adults
- Full DNA sequence analysis: 20 mL of whole blood in EDTA (anticoagulant) tubes (lavender top) or extracted DNA (50 µL with concentration of 200 ng/µL)
- For newborns or children
- Blood: 2 mL in pediatric EDTA tube (lavender top) or 2 mL in pediatric ACD tube (yellow top) from patient
- Ship at room temperature
- 10-14 days