Porphyria Cutanea Tarda (PCT)
PCT is a deficiency of the enzyme uroporphyrinogen decarboxylase. Cutaneous blisters develop 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. Neurological and abdominal symptoms are not characteristic of PCT. Liver function abnormalities are common, but are usually mild. PCT is often associated with hepatitis C infection, which also can cause these liver complications. However, liver tests are generally abnormal even in PCT patients without hepatitis C infection. Progression to cirrhosis and even liver cancer occurs in some patients.
Porphyria cutanea tarda (PCT) is the most common type of porphyria, with a prevalence of approximately 1 in 10,000. 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). Such individuals have inherited a URO-decarboxylase gene mutation from one parent, which has reduced the amount of URO-decarboxylase in all tissues from birth. However, to develop symptoms, other factors must be present to reduce URO-decarboxylase level in the liver to less than 20% of normal. Such f-PCT patients may develop blisters at an early age or have relatives with the disease. Excess iron and multiple other susceptibility factors contribute to the development of PCT. These include 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. A URO-decarboxylase inhibitor generated only in the liver accounts for the severely deficient enzyme activity in PCT. DNA analysis of the UROS 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 gene mutations listed in the Human Gene Mutation Database as well as novel mutations.
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, 83898x6, 83904x7, 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.