Porphyrias Flashcards
What are porphyrias?
7 disorders caused by deficiency in enzymes involved with haem biosynthesis
If these exist, toxic haem precursors build up
What enzyme is affected in plumboprophyria?
PBG synthase
Leading to accumulation of ALA
Symptoms of plumboporphyria?
Abdominal pain
Neurological symptoms e.g. coma, bulbar palsy
What enzyme does acute intermittent porphyria affect?
HMB synthase
leading to accumulation of PBG deaminase
5Ps - features of acute intermittent porphyrias?
Painful abdomen
Psychosis
Peripheral neuropathy
Port urine (red/brown urine)
How to diagnose Acute intermittent porphyrias?
High urinary levels *of PBG, low HMB activity in RBCs
- need to protect sample from light as in light it goes ‘port’ wine purple
How to manage acute intermittent porphyrias?
IV haem arginate
IC carbohydrate loading
What precipitating factors that can cause acute porphyrias?
ALA synthase inducers e.g. trimethoprim, nitrofurontoin, alcohol
Stress (infection, surgery)
Reduced caloric intake and endocrine factors e.g. before period
What enzyme is affecteed in hereditary coproporphyria
coproporphyrinogen oxidase
Symptoms seen in hereditary coproporphyria
Acute neurovisceral attacks:
photosensitvity lesions - blistering, skin fragility behind hands after sun
Urine PBG + prophyrins
What enzyme is affected in veriegate porphyria
protoprophyrinogen oxidase
What enzyme is affected in congenital erythropoietic porphyria?
Uroporphyrinogen III synthase
How does congenital erythropoietic porphyria present?
Non-blistering lesions
Photosensitivity, burning itching oedema,
What enzyme is affected in prophyria cutanea tarda?
Uroporphyrinogen decarboxylase
How does porphyria cutanea tarda present?
Vesicles on sun-exposed areas of skin crusting, superficial scarring and pigmentation
How is porphyria cutaenea tarda diagnosed?
Urinary uroporphyrins and coproporphyrins
-> pink red fluorescence with wood’s lamp
Increased ferritin
Abnormal LFTs
Which enzyme is affected by erythropoietic protoporphyria?
Ferrochetolase
Which porphyria is the most common?
Porphyria cutaenia tarda
(acquired version is due to liver disease e.g. HIV, Hep B)
How to diagnose erythropoietric protoporphyria?
Most common type in children
High RBC protoporphyrin IX
