Dermatology Porphyrias Flashcards
what is cutaneous photosensitivity?
an abnormal cutaneous response to UV radiation (and in some people, to visible light)
what are porphyrias?
group of disease in which substances called porphyrins build up - affecting the skin or nervous system. Most porphyrias are inherited and are due to a mutation in one of the genes that make haem.
acute intermittent porphyria
this is the type of porphyria that affects the nervous system. Inherited as autosomal dominant. Symptoms have rapid onset and last a short time. Symptoms include abdo pain, chest pain, vomiting, confusion, constipation, fever, high BP, tachycardia. Attacks last days to weeks.
what are some possible complications of AIP (acute intermittent porphyria)?
paralysis, hyponatremia, seizures.
Got increased risk of HCC, melanoma, lymphoma, chronic hypertension, chronic kidney disease, chronic pain
what can trigger attacks in AIP?
alcohol, smoking, hormonal changes, fasting, stress, drugs. If skin affected, blisters or itching may occur with sunlight exposure.
in the haem pathway, why do the upper metabolites (which are not porphyrins) not cause skin features?
it is only porphyrins (which appear in the latter half of the haem pathway) that react with visible light and can cause skin features.
what are some common porphyria skin features?
Skin disease is encountered where excess porphyrins accumulate in the skin. Porphyrins are photoactive and when exposed to light - they cause local skin damage. Features:
- blistering and fragility (vesiculo-erosive skin disease - blistering and erosions - but only in sun exposed areas).
- acute phototoxicity (about half an hour after sun exposure - got severe pain, burning, discomfort in exposed areas, redness, swelling of skin. But: typically, effects are NOT visible).
- (may have abnormal coloured teeth)
porphyria cutanea tarda (PCT) type 1
- presents with manifestations later in life
- results from low levels of enzyme responsible for the 5th step in haem production
- onycholysis, blistering in exposed areas, erosions (heal slowly and may scar), may get hyperpigmentation and hypertrichosis (especially on tops of cheeks), morphea (localised scleroderma), symptoms subside and recur.
- As well as skin disease, chronic liver problems are common in patients with SPORADIC form of PCT e.g. fibrosis, cirrhosis, hepatitis. BUT liver problems are LESS common in those with the INHERITED form of the disease.
- Patients often have a wine-red urine colour due to their enzyme deficiency.
- PCT is the most common porphyria
which enzyme is lacking in porphyria cutanea tarda (PCT)?
uroporphyrin decarboxylase (the 5th enzyme in the haem pathway)
if someone has PCT - disease in which internal organ should be suspected?
liver! (Their liver disease is the likely cause of the PCT)
Morphea is sometimes associated with PCT. What is morphea?
Morphea is a localised form of scleroderma. The skin, in places, is hardened (no internal organ involvement). Skin can become very tight. There may be poor blood flow to fingers.
how can a Wood’s lamp be used to diagnose PCT?
the Wood’s lamp gives off radiation - if you shine this light on the urine of a PCT patient - it gives off a pinky colour. (Wood’s lamp can also detect bacterial/ fungal skin infections, pigment disorders e.g. vitiligo, and other skin irregularities).
Management of PCT?
decide what the underlying cause is:
- alcohol?
- viral hepatitis?
- oestrogens?
- haemochromatosis?
Treat the underlying diseases and relieve the skin disease
erythropoietic protoporphyria (EPP)
erythropoietic protoporphyria is a form of porphyria which varies in severity and can be very painful. There is an enzyme deficiency which leads to abnormally high levels of protoporphyrin in RBCs, plasma, skin, liver.
There will be mild anaemia.
Protoporhyrin will react with light and cause pain.
People with erthropoietic protoporphyria become scared to go out in daylight - they get severe pain which can last whole day (get temporary pain relief from ice). Longer sun exposure may give them 2nd degree burns.
Repeated exposures: get lichenification, hypopigmentation, hyperpigmentation, scarring.
EPP usually first presents in childhood. If not as severe: manifests in puberty when hormones elevate.
what can trigger erythropoietic protoporphyria (EPP)?
sun exposure (even through glass)
