Porphyrias Flashcards
What are photodermatoses?
Skin disorders that are precipitated by exposure to sunlight.
What is photosensitivity?
An abnormal cutaneous response to UV radiation with/out visible light.
3 Types of Phototherapy
Broadband UVB, Narrow UVB, PUVA
What is PUVA?
Photochemotherapy, UVA radiation combines with a chemical sensitiser, psoralen.
Good clinical sign of photosensitivity
Sparing behind the ears.
What are porphyrias?
A group of diseases in which substances called porphyrins build up affecting the skin or nervous system.
Main groups of porphyrias
Phototoxic skin porphyrias
Blistering and skin porphyrias
Acute attack porphyrias
Severe congenital porphyrias
When does it manifest cutaneously?
Where excess porphyrins accumulate in the skin.
What are porphyrins?
Photoactive molecules and when exposed to light they cause local skin damage.
What are the 2 cutaneous patterns of disease?
Immediate photosensitivity.
Vesiculo-erosive skin disease.
What is immediate photosensitivity?
Usually 30mins after sun exposure. Severe burning pain, and discomfort in exposed areas. May have redness and swelling. But typically effects are not visible.
What is vesicle-erosive skin disease?
Blistering (vesicles) and erosions - but only in sun exposed areas. Mild disease consists of skin fragility in exposed ares with a tendency to form blisters or erosions which heal slowly.
Porphyria Cutanea Tarda is caused by
low levels of uroporphyrinogen decarboxylase.
Symptoms of porphyria cutanea tarda
oncholysis blistering in sun exposed areas heal slowly and scar hyperpigmentation hypertrichosis solar urticaria morphea
What is morphea?
Localised scleroderma that involves isolated patches of hardened skin on face, hands, and feet, with no internal organ involvement.
Thickened skin, stiffeness, poor blood flow to fingers.
Wine Red Coloured Urine
Porphyria Cutanea Tarda
Diagnosing protophyria cutanea tarda?
Woods lamp - shine light on urine of someone with PCT it gives it colour.
Management of PCT
Treat underlying cause, as it most likely due to liver disease.
What is Erythropoietic Protophoryia?
Deficiency in ferrochelatase.
Manifests at puberty, but first presents in childhood.
Symtoms of EP
Few minutes of exposure - pruritus, erythema, swelling, pain.
Longer exposure to sun in EP
2nd degree burns
Repeated sun exposure in EP
lichenification, hypperpigmentation, and scarring.
Protoporphyrin accumulating to toxic levels leads to
Lier failure
Investigations for EP
Quantitive RBC porphyrins fluorocytes transaminases red blood indices photo testing biliary tract USS.
