Porphyria Cutanea Tarda Flashcards
What is porphyria cutanea tarda (PCT)?
A disorder of heme metabolism caused by a deficiency of uroporphyrinogen decarboxylase (UROD), leading to the accumulation of porphyrins that cause photosensitivity and skin fragility.
What are the two main types of PCT?
Sporadic (type I): Acquired, most common form.
Familial (type II): Autosomal dominant, caused by a genetic mutation in the UROD gene.
What is the hallmark feature of PCT?
Photosensitivity with blistering and fragility on sun-exposed areas of the skin.
What enzyme deficiency causes PCT?
Deficiency of uroporphyrinogen decarboxylase (UROD) in the liver.
How does UROD deficiency lead to symptoms?
UROD deficiency causes accumulation of uroporphyrins and other porphyrins, which are photosensitizing, leading to oxidative damage in the skin upon UV exposure.
What are common triggers for sporadic PCT?
Alcohol consumption.
Estrogen use.
Hepatitis C virus (HCV).
Iron overload (e.g., hemochromatosis).
Smoking.
What are the characteristic skin findings in PCT?
Fragile, blistering lesions on sun-exposed areas (hands, forearms, face).
Erosions, crusts, and scarring after blisters rupture.
Hyperpigmentation or hypopigmentation.
Skin thickening or sclerodermoid changes in chronic cases.
How does PCT affect the nails and hair?
Nail fragility or onycholysis.
Hypertrichosis (excess hair growth) on the cheeks and temples.
How is PCT diagnosed?
Clinical suspicion: Based on characteristic skin findings.
Biochemical testing: Elevated uroporphyrins and heptacarboxyl porphyrins in urine.
Plasma fluorescence: Porphyrin fluorescence under Wood’s lamp.
Liver function tests: May show abnormalities if liver is involved.
What does a 24-hour urine test show in PCT?
Elevated uroporphyrins and coproporphyrins.
What is the first-line treatment for PCT?
Phlebotomy: Reduces iron stores and porphyrin production.
Low-dose hydroxychloroquine: Enhances porphyrin excretion.
How often are phlebotomies performed in PCT?
Every 1–2 weeks until ferritin levels normalize or symptoms improve.
What supportive care is important in PCT?
Strict sun protection (sunscreens, protective clothing).
Avoidance of alcohol, estrogen, and other triggers.
What are the potential complications of PCT?
Skin scarring and pigmentary changes.
Chronic liver disease or cirrhosis.
Increased risk of hepatocellular carcinoma.
Why is iron overload significant in PCT?
Excess iron exacerbates UROD deficiency and porphyrin accumulation, worsening symptoms.
