Write about Porphyrias here.

• 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