Extra Material on Porphyrias Flashcards
What forms the basis of all porphyrias?
Cells fails to change porphyrin and porphyrin precursors into haem
What is the difference between acute and cutaneous porphyrias?
Acute = largely affects nervous system Cutaneous = largely affects skin
What is the difference between erythropoietic and hepatic porphyrias?
Erythropoietic = bone marrow over produces porphyrin Hepatic = liver over produces porphyrin and it’s precursors
What enzyme is deficient in acute intermittent porphyria?
Porphobilinogen deaminase = causes porphyrin build up in liver
What enzyme is deficient in porphyria cutanea tarda?
Uroporphyrinogen decarboxylase = causes porphyrin build up in liver
What enzyme is deficient in erythropoietic protoporphyria?
Ferrochelatase = causes porphyrin build up in bone marrow
What is needed to cause symptoms in acute intermittent porphyrias?
Activating factor = after puberty, steroids, barbiturates, smoking, stress
What is the main symptom of acute intermittent porphyria?
Abdominal pain = may be severe or associated with nausea
What are some other symptoms of acute intermittent porphyrias?
Muscle weakness in limbs, agitation, insomnia, urinary retention
What are patients with acute intermittent porphyria at a higher risk of developing?
Hepatocellular carcinomas and kidney failure
What mutation causes acute intermittent porphyria?
Mutation in HMBS gene = inheritance is autosomal dominant
How is acute intermittent porphyria diagnosed?
Elevated urine ALA and porphobilinogen (PBG), PBGD deficiency in normal red blood cells
What is the main symptom of porphyria cutanea tarda?
Photosensitivity = painful blistering of sun exposed skin, skin fragility (May peel or blister on minor trauma)
How else may skin be affected on porphyria cutanea tarda?
Increased hair growth, thickening and darkening of skin
What other organ is affected by porphyria cutanea tarda?
Liver = increased risk of liver cirrhosis and carcinoma
What are some risk factors for developing porphyria cutanea tarda?
Excess iron, alcohol, smoking, oestrogen, chronic hepatitis C, HIV, mutations in HEF gene
What is a rare cause of porphyria cutanea tarda?
Familial inheritance = mutations in UROD gene, autosomal dominant
How may porphyria cutanea tarda be treated?
Regular phlebotomies
What mutation causes erythropoietic protoporphyrias?
Mutation in FECH gene = autosomal recessive inheritance
Where can FECH build up in erythropoietic porphyrias?
Bone marrow, red blood cells, blood plasma, skin and eventually liver
What can erythropoietic porphyria lead to?
Extreme sensitivity to sunlight, liver damage, abdominal pain, gallstones, splenomegaly
What are the common symptoms of erythropoietic porphyria?
Skin photosensitivity, erythema, pruritis
How is erythropoietic porphyria treated?
Sun avoidance and avoidance of UV exposure, vitamin D supplements, protective clothing, liver complications may need transplant
