Porphyria Cutanea Tarda – PCT

Pathophysiology and Triggers

Molecular Mechanisms in the Liver and Dermis

• UROD Enzyme Defect: In the heme synthesis pathway, UROD converts uroporphyrinogen to coproporphyrinogen. When UROD activity falls below 50%, the pathway stalls, and uroporphyrinogen accumulates and is oxidized to free uroporphyrin.
• Transport and Deposition in the Skin: Uroporphyrin is water-soluble. It travels from the liver into the blood and collects around superficial blood vessel walls and at the dermal–epidermal junction.
• Soret Band Phototoxicity:
  • Uroporphyrin absorbs most strongly at visible wavelengths of 400–410 nm (the Soret band).
  • This absorbed energy generates reactive oxygen species (ROS) and singlet oxygen, which directly damage endothelial cell membranes and break down type IV and VII collagen at the basement membrane.
  • Serum leaks out of the vessels, separating the epidermis from the dermis and forming deep, non-inflammatory blisters.

Types and Triggers

PCT has two main forms:

• Acquired PCT (Type I, Sporadic): About 80% of cases. There is no inherited mutation, but hepatic UROD is inactivated by external toxic factors.
• Inherited PCT (Type II, Familial): About 20% of cases. Patients carry a heterozygous UROD mutation, inherited in an autosomal dominant pattern with low penetrance. They have 50% less enzyme from birth, and symptoms flare when a trigger is encountered.

The main triggers of PCT include:

• Hepatic Iron Overload: Excess iron catalyzes free-radical formation that directly inhibits UROD. HFE gene mutations (hemochromatosis) are found in more than 50% of PCT patients.
• Hepatitis C Virus (HCV) Infection: HCV causes chronic hepatitis, disturbs lipid metabolism and suppresses UROD synthesis.
• Alcohol Misuse: Alcohol increases intestinal iron absorption and stimulates ALAS1, the first enzyme in the pathway, boosting production of porphyrin precursors.
• Estrogen Therapy: Oral contraceptives or hormone replacement therapy in women alter the liver's metabolic function.

Characteristic Clinical Features of PCT

PCT mainly affects sun-exposed skin such as the backs of the hands, forearms, face, neck and toes.

Acute and Subacute Signs

• Skin Fragility: The skin is extremely delicate. A light knock or accidental rub can shear the epidermis off the dermis, leaving a shallow erosion.
• Tense Bullae: Blisters arise on normal-looking skin (no redness or inflammation) and contain clear or blood-stained fluid. Once they break, they leave weeping erosions that crust over thickly.
• Dark Urine: Urine turns dark red, strong-tea colored or wine-colored because large amounts of uroporphyrin are excreted by the kidneys.

Chronic Changes and Sequelae

• Milia and Atrophic Scars: Healed blister sites develop many small, opaque white bumps (milia), along with thin, flat atrophic scars and mottled hyper- or hypopigmentation.
• Facial Hypertrichosis: Seen in more than 70% of patients. Fine facial hair grows longer, darker and thicker, especially on the temples, cheeks, hairline and eyebrows.
• Sclerodermoid Plaques: Skin on the neck, chest, upper back or cheeks becomes hardened and thickened, with an ivory or yellow-gray color closely resembling scleroderma.

Our Diagnostic Process at Haute-Derma

To confirm PCT and identify its root cause, Haute-Derma uses a comprehensive workup:

Fluorescence and Biochemical Testing

• Wood's Lamp Examination of Urine: Under a Wood's lamp (365 nm), a fresh, acidified urine sample glows bright pink or orange-red.
• Plasma Fluorescence Spectroscopy: Plasma fluorescence is measured with excitation at 400 nm. PCT shows a characteristic emission peak at 618–620 nm.
• 24-Hour Urine Porphyrins: Uroporphyrin I and III are markedly elevated relative to coproporphyrin (uro:copro ratio > 3:1).

Skin Histopathology and Direct Immunofluorescence (DIF)

• Histopathology: The blister is entirely subepidermal, with very few inflammatory cells inside. Dermal papillae project up into the blister cavity, giving the characteristic "festooning" pattern.
• Direct Immunofluorescence: Band-like deposits of IgG, IgM and complement C3 around superficial dermal capillary walls and along the basement membrane zone.

Risk Factor Screening

• Iron Studies: Serum ferritin, serum iron and transferrin saturation.
• Viral Screening: Anti-HCV antibodies, HBsAg and HIV.
• Liver Function Assessment: ALT, AST, GGT and bilirubin levels, plus liver elastography.

PCT Treatment Protocol at Haute-Derma

The goals of PCT treatment are to clear excess porphyrins from the body, bring ferritin down to an optimal level and fully address the triggers.

Therapeutic Phlebotomy

• Indication: First-line treatment for patients with high serum ferritin (> 200 ng/mL).
• Mechanism: Removing blood depletes liver iron stores, releasing UROD from iron-mediated inhibition.
• Procedure: 400–500 mL of blood is removed every 2 weeks. Treatment is paused once serum ferritin falls to 20–50 ng/mL or hemoglobin drops below 11 g/dL. Most patients achieve full remission after 5–6 sessions.

Low-Dose Antimalarials

• Indication: For patients who cannot undergo phlebotomy (anemia, heart disease, frailty) or who have normal ferritin.
• Dosage: Hydroxychloroquine 100 mg by mouth twice weekly (on fixed days, e.g., Monday and Thursday) or chloroquine 125 mg by mouth twice weekly.
• Mechanism: At very low doses, hydroxychloroquine binds uroporphyrin in the liver, forming a soluble complex that is readily excreted in the urine.
• Important Caution: Standard high doses (200–400 mg/day) must never be used, as they release porphyrins massively and can cause acute liver cell necrosis.

Managing Triggers and Sun Protection

• Hepatitis C Treatment: Direct-acting antivirals (DAAs) such as sofosbuvir/velpatasvir for 12 weeks clear HCV and help bring PCT into remission.
• Targeted Sun Protection: Ordinary sunscreens (SPF/PA) do not block the Soret band (400–410 nm). Patients need a tinted mineral sunscreen containing iron oxides combined with micronized zinc oxide to shield against this visible light range.