Table 1

Distinguishing features of the acute hepatic porphyrias

Type of porphyria	Enzyme deficiency	Gene	Incidence per million*	Clinical presentation	Increased haem pathway metabolites
ALA dehydratase porphyria	ALA dehydratase	ALAD	Exceptionally rare†	Acute attacks	Urine: ALA Red cell: zinc protoporphyrin
Acute intermittent porphyria	Hydroxymethylbilane synthase	HMBS	0.13	Acute attacks	Urine: ALA, PBG, uro Faeces: copro III:I ratio normal Plasma: FEP at 615–622 nm
Hereditary coproporphyria	Coproporphyrinogen oxidase	CPOX	0.02	Acute attacks and/or bullae and skin fragility	Urine: ALA, PBG, copro III Faeces: copro III:I ratio>1.5 Plasma: FEP at 615–622 nm
Variegate porphyria	Protoporphyrinogen oxidase	PPOX	0.08	Acute attacks and/or bullae and skin fragility	Urine: ALA, PBG, copro III Faeces: copro III:I ratio>1.5, proto>copro Plasma: FEP at 624–628 nm

*Symptomatic incidence in European population.16
†Only eight cases reported to date.3
ALA, aminolevulinic acid; ALAD, 5-aminolaevulinic acid dehydratase; copro, coproporphyrin; FEP, fluorescence emission peak; PBG, porphobilinogen; proto, protoporphyrin; uro, uroporphyrin.