Porphyria Cutanea Tarda (PCT)

Related Subjects: | Acute Porphyrias | Variegate Porphyria | Acute Intermittent Porphyria (AIP) | Porphyria Cutanea Tarda (PCT) | Porphyria Testing

PCT causes blistering of the backs of hands and the forehead which usually heals with a small scar and milia formation. Autosomal dominant inheritance of a single mutation of the UROD gene.

About

• Porphyrins produced in PCT are photoactive molecules that absorb light energy strongly in the visible violet spectrum.
• Photoexcited porphyrins in the skin mediate oxidative damage to biomolecular targets, causing cutaneous photosensitivity reactions.

Aetiology

• Deficient activity of the heme-synthetic enzyme uroporphyrinogen decarboxylase (URO-D) in the liver.
• 80% of all cases are acquired; 20% are familial
• Autosomal dominant inheritence
• Overproduction of porphyrins accumulate in the liver and plasma

Clinical

• Blistering Photosensitive eruption worsens to light exposure
• Hypertrichosis and milia formation (keratin-containing cysts)
• Fragility of sun-exposed skin after mechanical trauma
• Leads to erosions and bullae, worst on dorsal hands, forearms and face

Investigations

• Urinary porphyrin levels are high in PCT in a 24-hour period. The porphyrin pigment is often grossly evident in visible light and yields a pink fluorescence under Wood lamp (black light) radiation
• Faecal coproporphyrin fraction is often abnormally high
• Measure UROD enzyme activity assay in red blood cells where available

Management

• Avoid sunlight, alcohol and smoking and oestrogens
• Therapeutic phlebotomy reduces iron stores, which improves heme synthesis disturbed by Ferro-mediated inhibition of uroporphyrinogen decarboxylase (UROD).
• The goal of therapy is to reduce serum ferritin levels to the lower limit of the reference range. Ensure Hb > 11 g/dl.
• Oral chloroquine phosphate or hydroxychloroquine sulfate can be effective.
• Chelation with desferrioxamine is an alternative means of iron mobilization when venesections are not practical.

All samples collected must be protected from light. Collection Bottles: Blood - Purple EDTA, Urine - White plain 20ml universal, Faeces - Blue Faecal 20 ml universal