Porphyrias

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• Group of rare inborn errors of metabolism

• Abnormalities of enzymes involved in the biosynthesis of haem, resulting in the overproduction of the intermediate compounds called 'porphyrins'.

• Extreme heterogeneity

• Chief limiting step in haem production is -ALA synthetase, with an increase in the is enzyme resulting in an overproduction of porphyrins.

• Haem provides a negative feedback mechanism for the enzyme

• The excess porphyrins are produced in either the liver (Hepatic Porphyria) or in the bone marrow (Erythropoietic Porphyria)

• Two main types - acute and nonacute


Acute Porphyria


Non-Acute Porphyria