Porphyria - Anaemias

Porphyria

·        Disorder of haem synthesis ® toxic metabolites 

·        Many types, all due to genetic deficiency. Homozygous not viable. Heterozygotes can produce enough haem, but when the system is challenged ® ­ toxic metabolites

·        Symptoms:

o   Uncommon, but differential in intermittent abdominal pain

o   Can be intermittent or constant

o   Can acutely cause psychotic symptoms

o   Sun sensitivity (accumulation of metabolites in skin)

o   Neuro-visceral symptoms (pain but no organ pathology)

o   Rare types can cause sideroblastic anaemia

·        Investigations:

o   Urine test for metabolites (porphyrins)

o   Then specific test for which porphyria

·        ALA synthase controls the rate limiting step at the beginning of the pathway: 

o   Induced by: BZDs, alcohol, oestrogen and progesterone (® onset at puberty or on starting the OCP), sulphonamides, tetracycline, theophylline 

o   Inhibited by haem, glucose