Porphyria Cutanea Tarda
Related Gene(s): UROD
Porphyria cutanea tarda (PCT) is a deficiency of the enzyme uroporphyrinogen decarboxylase in the heme biosynthesis pathway. It is the most common type of porphyria, with a prevalence of approximately 1 in 10,000 people. PCT develops when the activity of the enzyme uroporphyrinogen decarboxylase (URO-decarboxylase) becomes severely deficient (less than 20% of normal) in the liver. In most cases, these patients do not have URO-decarboxylase gene mutations and are said to have sporadic (or Type I) PCT (s-PCT), About 20 percent of cases have familial (or Type II) PCT (f-PCT), where an individual inherits a URO-decarboxylase gene mutation from one parent. This reduces the amount of URO-decarboxylase in all tissues from birth. However, other factors must be present to reduce URO-decarboxylase level in the liver to less than 20% of normal. Other factors that may contribute to the development of PCT include excess iron, the use of alcohol or estrogens, smoking, chronic hepatitis C, HIV (human immunodeficiency virus), and mutations of the HFE gene, which is associated with the disease hemochromatosis. Other factors remain to be identified.
People with PCT may develop cutaneous blisters on sun-exposed areas of the skin, such as the hands and face. The skin in these areas may blister or peel after minor trauma. Increased hair growth, as well as darkening and thickening of the skin, may also occur. Liver function abnormalities are common, but are usually mild. PCT is often associated with hepatitis C infection, which can also cause these liver complications. Progression to cirrhosis and even liver cancer may occur in some patients.
DNA analysis of the UROD 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 >97% of gene mutations reported in the Human Gene Mutation Database, as well as novel mutations.
Prenatal diagnosis is also available. Prior to ordering prenatal testing, please contact our laboratory at 800.298.6470 to discuss.
- Testing requires prior documentation of parental mutations.
- Chorionic villi: 5-10 mg in conical tube with sterile saline or transport media
- Amniotic fluid: 10 mL in conical tube
- Cultured cells: Two confluent T-25 flasks
- Additionally, please send:
- Maternal blood: 5-10 mL in EDTA tube (lavender top) required to perform MCC studies on all prenatal samples and in case maternal confirmation studies are necessary
- Paternal blood: 5-10 mL in EDTA tube (lavender top) in case paternal confirmation studies are necessary
- For adults
- Full DNA sequence analysis: 10-20 mL of whole blood in EDTA (anticoagulant) tubes (lavender top) or extracted DNA (50 µL with concentration of 200 ng/µL)
- Targeting mutation analysis: 20 mL of whole blood in EDTA (anticoagulant) tubes (lavender top) or extracted DNA (30 µL with concentration of 200 ng/µL) or buccal cells (buccal brushes must be requested from laboratory)
- 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
- Prenatal: 3-5 days
- Postnatal: 10-14 days