Porphyrias Flashcards
What are the porphyrias?
7 disorders caused by a deficiency in enzymes involved in haem biosynthesis, leading to a build-up of toxic haem precursors
What is the mode of inheritance of acute intermittent porphyria?
Autosomal dominant
Name the enzyme affected in acute intermittent porphyria
Hydroxymethylbilane (HMB) synthase
What are the symptoms of acute intermittent porphyria?
Abdominal pain, seizures, psychiatric disturbance, nausea, vomiting, tachycardia, hypertension, sensory loss, muscle weakness, constipation, urinary incontinence
Which porphyria has no skin involvement?
Acute intermittent porphyria
How is acute intermittent porphyria diagnosed?
ALA and PBG in urine (port-wine urine)
Name three precipitants of episodes of acute intermittent porphyria
ALA synthase inducers, stress, reduced caloric intake, endocrine factors (e.g. pre-menstruation)
Name three ALA synthase inducers
Steroids, ethanol, barbiturates
How is acute intermittent porphyria treated?
Avoid precipitating factors, analgesia, IV carbohydrate or haem arginate
Name two acute porphyrias with skin lesions
Hereditary coproporphyria (HCP), variegate porphyria (VP)
What is the mode of inheritance of HCP?
Autosomal dominant
What is the mode of inheritance of VP?
Autosomal dominant
What are the symptoms of HCP?
Neurovisceral and skin lesions
How is HCP diagnosed?
Raised porphyrins in faeces or urine
Name three non-acute porphyrias
Congenital erythropoietic porphyria (CEP), erythropoietic protoporphyria (EPP), porphyria cutanea tarda (PCT)
