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514 Chapter 13: Nutritional and metabolic disorders

substance that stains pink on haematoxylin and eosin Porphyria
and stains red with Congo red.
Definition
Management Theporphyriasaregeneticoracquireddeficienciesinthe
Therapy is aimed at the underlying cause where possi- activity of enzymes in the heme biosynthetic pathway.
ble such as inflammation, infection or blood dyscrasia.
Differing manifestations such as renal failure require Aetiology/pathophysiology
support.Inthehereditaryamyloidoseswheretheprecur- Heme is synthesised from succinyl Co A and glycine (see
sor protein is produced by the liver, liver transplantation Fig 13.2); differing enzyme deficiencies cause different
is curative. patterns of disease.

Succinyl Co A & Glycine

ALA synthetase

Aminolaevulinic Acid (ALA)

PBG synthetase

Porobilinogen (PBG)
PBG deaminase
Deficiency causes acute intermittent porphyria
Hydroxymethylbilane (HMB)
UPP III cosynthetase
Deficiency causes congenital crythropetic porphyria

Uroporphyrinogen I Uroporphyrinogen III

Uroporphyrogen decarboxylase
Deficiency causes porphyria cutanea tarda

Coproporphyrinogen I Coproporphyrinogen III
Coproporphyringoen oxidase
Deficiency causes hereditary coprpophyria

Protophyrinogen

Ferrochelatase
Deficiency causes erythropoetic protoporphyria

Heme

Figure 13.2 Heme synthesis.