Photosensitivity And Porphyria Flashcards
What is photosensitivity?
Skin disorders that stem from normal levels of UV light
What are the different types of photosensitivity disorders?
-Immunological/idiopathic
-Drugs (that sensitise the skin to light)
-Endogenous (porphyria)
-Photogenodermatoses (XP, RT, Bloom)
-Photoaggravated (pre existing conditions that are made worse by light)
What is XP?
Xeroderma pigmentosum
Rare autosomal recessive disorder that causes severe photosensitivity from a young age
How severe is XP and how is it managed?
Managed with strict sun avoidance
High mortality rate -> very early formation of skin cancers
What are some examples of immunological/idiopathic photosensitivity conditions?
polymorphic light eruption
Actinic prurigo
Chronic actinic dermatitis
Solar urticaria
What is PLE?
Polymorphic light eruption
Recurrent abnormal reaction to sunlight or artificial radiation
Seasonal
Type IV hypersensitivity + resistant langerhans cells
What is actinic prurigo?
Rare HLA linked condition
More severe form of PLE, all year round as opposed to seasonal
What is chronic actinic dermatitis?
Light sensitivity disorder that presents like eczema
What is solar urticaria
Hives triggered by UV exposure
IgE mediated so immediate
What drugs can cause photosensitivity
Thiazide diuretics
Amiodarone
Tetracyclines
Quiniolones
Antipsychotics eg chloropromazine
What is porphyria?
Photosensitivity disorders caused by an inherited or acquired defect in the enzymes needed to produce haem:
Accumulation of these porphyrins make u photosensitive
What are the main types of porphyria?
Acute intermittent
Porphyria cutanea tarda
Erythropeotic protoprophyria
What is acute intermittent porphyria?
Who gets it?
how does it present?
Porphobillinogen deaminase deficiency
Porphobillinogen accumulates
Presents in females around age 30
Acute abdominal pain
Mood disturbance
Neuro symptoms and seizures
What is porphyria cutanea tarda?
Who gets it?
How does it present?
Uroporphyrinogen decarboxylase deficiency,
uroporphyrinogen accumulates
Most common type, usually seen in middle aged men
Associated with liver disease, so signs of liver disease may be seen
Presents with blistering lesions on sun exposed areas, that heal with scarring
Solar urticaria
Hypertrihosis
Skin thickening (morphoea)
How is Porphyria cutanea tarda investigated and managed?
Bloods- porphyrin studies
Woods lamp- urine shines pink instead of blue
Treat underlying cause- ie alcohol, viral hepatitis, haemachromatosis
What is Erythropeotic protoprophyria?
Who gets it?
Autosomal dominant
ferrochelatase deficiency -> protoporphyrin IX accumulates
Common in children
How does Erythropeotic protoprophyria present?
No rash, BUT skin will burn and itch on sun exposure
Typical pres: Child will scream when placed in sun
How is Erythropeotic protoprophyria investigated and managed?
RBC poryphins
Transaminases
Hub
Biliary tract USS
Phototesting
6 monthly LFTs and RBC porphrins
Photoprotection measures
Prophylactic TL-01 phototherapy
Antioxidants
Avoid iron
Incipient liver failure - oral charcoal, cholestyramine, ASA synthase inhibition
Liver failure - liver transplant
