Week 1 - F - Porphyrias - Porphyria cutanea tarda (adult), erythropoietic protoporphyria (child), acute intermittent protoporhyia Flashcards
Define photosensitivity?
Photosensitivity is the abnormal cutaneous response to ultraviolet radiation and in some individuals visible light
What is a porphyria? What is porphyrin essential in?
Porphyrias are a group of disorders that are caused by different erros in haem biosynthesis resulting in the build up of natural chemicals that produce porphyrin in the body Prophyrin is a component in haemoglobin - porphyrin ring + iron = heme + O2 = haemoglobin
The build up of porphyrins in the body can cause different symptoms depending on the different stage in the haemo biosynthesis that is interrupted What are the main groups of porphyrias? (not the types, just the overall group)
* Phototoxic skin porphyrias * Bistering and fragility skin porphyrias * Acute attack porphyrias - some with skin involvement and some without * Severe congenital porphyrias
Depending on the stage in haem biosynthesis that is faulty, there is the accumulation of either porphyrinogens, which are unstable and oxidise to porphyrins, or their precursors, porphobilinogen and delta-aminolaevulinic acid What is the difference ins symptoms caused by porphyrins and porphyrin precursors?
Porphyrins induce photosensitivity and the formation of toxic free radicals Porphyrin precursors (porphobilinogen and delta-aminolaevunic acid) are neurotoxic
What are the three main type of porphyria? Which is most common?
Erythropoietic protoporphyira Porphyria cutanea tarda Acute intermittent porphyria Porphyria cutanea tarda is the most common type of porphyria
What causes porphyria cutaena tarda and what does it cause a build up of?
Porphyria cutanea tarda is caused by a deficinecy in uroporphyrinogen decarboxylase (UROD) This causes a build up in uroporphyrinogen III
What is the typical presentation of a patient with PCT? What age? How is it diagnosed?
Typical presentation is Adult presenting with blistering skin lesions and fragility Also has facial hypertrichosis (abnormal growth of hair - usually on cheeks) and hyperpigmentation
How is porphyria cutanea tarda diagnosed?
Diagnosed by measuring an increase in porphyrin Can be shown using Wood’s lamp - this is where you use black light to show the pink flouresence of the porphyrin
What conditions are associated with prophyria cutanea tarda and therefore must be considered when diagnosing the condition?
* Hepatitis C * Haemochromatosis - excessive iron absorption means body needs more heme, therefore more build up of uroporphyrinogen III due to the dysfunctioning enzyme (uroporphyrinogen decarboxylase) * Alcohol abuse
Management of PCT includes managing the underling cause once found What is the management of the symptoms?
Sun avoidance or protection
What deficiency causes erythropoeitic protoporphyria? What does it cause a build up of/
Erythropoeitic protoporphyria is where there is a deficiency in the enzyme ferrocheletase causing a build up of protoporphyin IX (final step in haem biosynthesis)
How does erythropoeitic protoporphyria present? What age?
EPP usually presents in childhood with a child crying in direct sunlight due to burning, itching and scarring of the skin A few minutes of exposure to the sun induces pruritus, erythema, swelling and pain. Longer periods of exposure may induce second degree burns
How is EPP diagnosed?
It is often diagnosed by measuring the presence of circulating fluorescent red blood cells (fluorocytes) viewed under ultraviolet light
What is the treatment of EPP? What is measured every 6 months?
Treatment usually involves photoprotection measures - eg avoiding sunlight, wearing clothing to cover the skin, topical sunscreen Protoporphyrin IX levels can accumulate and cause liver failure so 6 monthly LFTs and RBC porphyrins are carried out
What enzyme deficinecy cause acute intermittent protoporphyria? What is there a build up of?
Deficiency in the enzyme porphobilinogen deaminase and there is therefore a build up of porphobilinogen (remember this and delta-aminolaevulinnc acid are neurotoxic)
