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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Hepatology

The Biology of PCT: Sporadic vs. Familial

At a Glance

Porphyria Cutanea Tarda (PCT) has two forms: sporadic (acquired) and familial (inherited). Both are caused by UROD enzyme deficiency and cause identical skin symptoms. However, neither type typically causes symptoms without an unmasking trigger like iron overload, Hepatitis C, or alcohol use.

All forms of Porphyria Cutanea Tarda (PCT) result from a problem with the same “worker” in your body’s heme production line: the UROD enzyme [1]. However, the reason why that enzyme stops working can differ. Doctors categorize PCT into two main types based on whether the deficiency is something you were born with or something you acquired.

The Two Faces of PCT

While the biological cause differs, it is important to know that Type 1 and Type 2 PCT look and act exactly the same on the skin [2]. Your treatment will likely be identical regardless of which type you have [3].

Feature Sporadic (Type 1) Familial (Type 2)
Frequency ~80% of cases [4] ~20% of cases [4]
Origin Acquired during life Inherited from a parent
Enzyme Location Deficiency only in the liver [4] Deficiency in all tissues (including red blood cells) [5]
Genetic Test No inherited UROD mutation [4] Positive for UROD gene mutation [4]

Type 1: Sporadic PCT

Sporadic PCT is the most common form. In this type, you were born with perfectly healthy UROD genes. However, over time, a combination of “unmasking factors” caused the enzyme in your liver to become inactive [6]. Because the issue is limited to the liver, your red blood cells will typically show normal enzyme activity [4].

Type 2: Familial PCT

Familial PCT is caused by an inherited mutation in one of your two UROD genes [4]. This mutation is passed down in an autosomal dominant pattern, meaning if one parent has the mutation, there is a 50% chance each child will inherit it [5].

In Type 2, every cell in your body starts with only about 50% of the normal enzyme activity [7]. However, even with only half the enzyme working, most people with this mutation never develop symptoms [4]. The mutation alone is usually not enough to cause the disease; it simply makes you more sensitive to triggers.

The “Trigger” Requirement

Whether you have Type 1 or Type 2, PCT almost always stays “hidden” until it is unmasked by specific lifestyle or health factors. These triggers interfere with the liver’s remaining enzyme activity, pushing it below the critical level needed to process porphyrins [3].

Common unmasking factors include:

  • Iron Overload: High levels of iron in the liver are the most common trigger [8][9].
  • Hepatitis C: This virus can directly interfere with how the liver handles porphyrins [10][11].
  • Alcohol & Smoking: Both can stress the liver and contribute to enzyme inactivation [12][3].
  • Estrogen: Hormonal medications, such as birth control or hormone replacement therapy, can also unmask the condition [13].

Should My Family Be Tested?

If you are diagnosed with Type 2 PCT, it means you carry a genetic susceptibility. Your doctor may suggest measuring the UROD enzyme activity in your red blood cells or performing genetic testing to confirm the type [4][5]. If Type 2 is confirmed, your close relatives (parents, siblings, and children) may choose to be tested to see if they also carry the susceptibility, even if they have no symptoms.

Common questions in this guide

What is the difference between Type 1 and Type 2 PCT?
Type 1 (sporadic) is acquired during your life and affects the UROD enzyme only in your liver. Type 2 (familial) is inherited from a parent and causes lower enzyme activity in every cell of your body.
Do Type 1 and Type 2 PCT have different symptoms or treatments?
No, both forms of porphyria cutanea tarda look and act exactly the same on the skin. The treatment approach is also typically identical regardless of whether your condition is sporadic or familial.
If I have the Type 2 PCT mutation, will I definitely get symptoms?
Having the inherited mutation alone is usually not enough to cause the disease. Most people with the genetic susceptibility never develop symptoms unless unmasking factors like iron overload, alcohol use, or estrogen medications trigger the condition.
What triggers Porphyria Cutanea Tarda symptoms?
PCT symptoms are typically unmasked by factors that stress the liver and further lower UROD enzyme activity. Common triggers include high iron levels, Hepatitis C infection, alcohol consumption, smoking, and estrogen-based medications.
Should my family members be tested for PCT?
If you are diagnosed with the familial form of PCT, your close relatives may choose to undergo genetic or biochemical testing. This can identify if they carry the same genetic susceptibility, even if they currently have no symptoms.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my history, do you think I have Type 1 or Type 2 PCT?
  2. 2.Should I have my red blood cell UROD activity measured to see if this runs in my family?
  3. 3.If I have Type 2, what is the likelihood that my children will also develop the disease?
  4. 4.Do I need genetic testing for the UROD gene, or is biochemical testing sufficient?
  5. 5.Does knowing my type change my treatment plan or how we manage my triggers?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (13)
  1. 1

    A Case Report of Porphyria Cutanea Tarda with Hepatitis-C Virus Co-infection.

    Hasan MN, Bhuiyan MR, Ferdous SH, et al.

    Mymensingh medical journal : MMJ 2023; (32(2)):584-586.

    PMID: 37002774
  2. 2

    Urinary metabolic profiling of asymptomatic acute intermittent porphyria using a rule-mining-based algorithm.

    Luck M, Schmitt C, Talbi N, et al.

    Metabolomics : Official journal of the Metabolomic Society 2018; (14(1)):10 doi:10.1007/s11306-017-1305-9.

    PMID: 29416446
  3. 3

    Porphyria cutanea tarda: Recent update.

    Singal AK

    Molecular genetics and metabolism 2019; (128(3)):271-281 doi:10.1016/j.ymgme.2019.01.004.

    PMID: 30683557
  4. 4

    Porphyria cutanea tarda and hepatoerythropoietic porphyria: Identification of 19 novel uroporphyrinogen III decarboxylase mutations.

    Weiss Y, Chen B, Yasuda M, et al.

    Molecular genetics and metabolism 2019; (128(3)):363-366 doi:10.1016/j.ymgme.2018.11.013.

    PMID: 30514647
  5. 5

    Novel UROD mutation for porphyria cutanea tarda, type 2: a case report.

    Soufleris S, Moore M, Phillips JD, et al.

    AME case reports 2024; (8()):67 doi:10.21037/acr-23-66.

    PMID: 39091564
  6. 6

    Blistering Disease During the Treatment of Chronic Hepatitis C With Ledipasvir/Sofosbuvir.

    Cash J, Skinner A, Cash S, et al.

    Federal practitioner : for the health care professionals of the VA, DoD, and PHS 2019; (36(Suppl 2)):S11-S13.

    PMID: 30983856
  7. 7

    The D519G Polymorphism of Glyceronephosphate O-Acyltransferase Is a Risk Factor for Familial Porphyria Cutanea Tarda.

    Farrell CP, Overbey JR, Naik H, et al.

    PloS one 2016; (11(9)):e0163322 doi:10.1371/journal.pone.0163322.

    PMID: 27661980
  8. 8

    Porphyria cutanea tarda: a unique iron-related disorder.

    Leaf RK, Dickey AK

    Hematology. American Society of Hematology. Education Program 2024; (2024(1)):450-456 doi:10.1182/hematology.2024000664.

    PMID: 39644053
  9. 9

    [Porphyria cutanea tarda].

    Mistegård J, Christiansen AL, Vestergaard C, et al.

    Ugeskrift for laeger 2025; (187(38)) doi:10.61409/V11240832.

    PMID: 41025764
  10. 10

    Evolution of HCV associated porphyria cutanea tarda after HCV sustained virologic response by direct acting antivirals.

    García-Fraile LJ, García-Buey L, Alonso Cerezo C, et al.

    Gastroenterologia y hepatologia 2022; (45(4)):249-255 doi:10.1016/j.gastrohep.2021.09.001.

    PMID: 34562521
  11. 11

    Ledipasvir/Sofosbuvir Is Effective as Sole Treatment of Porphyria Cutanea Tarda with Chronic Hepatitis C.

    Bonkovsky HL, Rudnick SP, Ma CD, et al.

    Digestive diseases and sciences 2023; (68(6)):2738-2746 doi:10.1007/s10620-023-07859-8.

    PMID: 36811718
  12. 12

    Human Immunodeficiency Virus Associated Sporadic Nonfamilial Porphyria Cutanea Tarda.

    Guha SK, Bandyopadhyay D, Saha A, Lal NR

    Indian journal of dermatology 2016; (61(3)):318-20 doi:10.4103/0019-5154.182424.

    PMID: 27293254
  13. 13

    Porphyria cutanea tarda precipitated by ovarian stimulation during oocyte retrieval in a genetically susceptible female.

    Rasheed E, Savage S, Walsh E, et al.

    Annals of clinical biochemistry 2021; (58(3)):251-256 doi:10.1177/0004563220988037.

    PMID: 33393347

This page provides educational information about the genetic and acquired forms of Porphyria Cutanea Tarda. Always consult your doctor or a genetic counselor to interpret your specific lab results or family testing needs.

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