Photodermatology and Porphyrias

Question 1

What are the main group of porphyrias?

Answer 1

Phototoxic skin porphyrias (such as erythropoietic protoporphyria)
Blistering and fragility skin porphyrias
Acute attack porphyrias (some with no skin involvement; some also cause blistering and fragility)
Severe congenital porphyrias (such as congenital erythropoetic porphyria)

Question 2

What enzyme disruption causes porphyria cutanea tarda?

Answer 2

Uroporphyrinogen decarboxylase

Question 3

What are the typical presentations of porphyria cutanea tarda?

Answer 3

Blisters, fragility, hyperpigmentation, hypertrichosis, solar urticarial, morphoea

Question 4

What investigations are involved in diagnosing porphyria cutanea tarda?

Answer 4

Woods lamp (wavelength tests)

Question 5

What is involved in the management of pct?

Answer 5

Find underlying cause: alcohol , viral hepatitis, oestrogens, haemochromatosis. Treatment aim: relieve disease, treat underlying disease

Question 6

Which enzyme deficiency causes erythropoietic protoporphyria?

Answer 6

Ferrochelatase

Question 7

What investigations are involved in EPP?

Answer 7

Quantitative RBC porphyrins, fluorocytes (patient, relatives), transaminases, [Hb], red cell indices, biliary tract USS, phototesting

Question 8

What is the management of EPP?

Answer 8

Explain diagnosis; (genetic counselling)
6 monthly LFTs and RBC porphyrins

Visible light photoprotection measures (particular need for caution if surgery needed)

Prophylactic TL-01 phototherapy
Anti-oxidants (beta-carotene, cysteine, high dose vitamin C)
(Avoid iron)

Incipient liver failure: oral charcoal; cholestyramine; ? ALA synthase inhibition
Liver failure: transplant liver; ? Bone marrow

Question 9

What are some findings that may suggest a ddx including acute intermittent porphyria?

Answer 9

Acute abdomen, mononeuritis multiplex, Guillian Barre Syndrome. Psychoses

Question 10

What enzyme deficiency causes AIP?

Answer 10

Porphobilinogen deaminase