Differentials
Variegate porphyria (VP)
SIGNS / SYMPTOMS
Blistering skin lesions are common and identical to PCT. Abdominal pain and other neuropathic manifestations are other symptoms of VP.
Hereditary coproporphyria (HCP)
SIGNS / SYMPTOMS
Blistering skin lesions identical to PCT, but less common than in VP. Abdominal pain and other neuropathic manifestations are other symptoms of HCP.
INVESTIGATIONS
Urinary and faecal porphyrins in HCP are predominantly coproporphyrin III. Urinary porphyrin precursors may be elevated.
Congenital erythropoietic porphyria (CEP)
SIGNS / SYMPTOMS
More severe blistering skin lesions in moderate to severe CEP. Mild CEP can resemble PCT.
INVESTIGATIONS
Substantial elevation in erythrocyte porphyrins. Urinary porphyrins predominantly uroporphyrin I and coproporphyrin I and faecal porphyrins coproporphyrin I.
Pseudoporphyria
SIGNS / SYMPTOMS
Blistering skin lesions over sun-exposed areas identical to those in PCT. A photosensitising drug can be identified in some instances.
INVESTIGATIONS
Plasma porphyrin levels normal.
Hepatoerythropoietic porphyria
SIGNS / SYMPTOMS
Usually begins in early childhood and resembles congenital erythropoietic porphyria.
INVESTIGATIONS
Marked elevations of erythrocyte porphyrins as well as urinary and plasma uroporphyrin and heptacarboxyl porphyrin. Erythrocyte uroporphyrinogen decarboxylase (UROD) activity <10% of normal. Homozygous or compound heterozygous UROD mutations.
Homozygous forms of acute porphyrias
SIGNS / SYMPTOMS
Usually begin in early childhood and resemble congenital erythropoietic porphyria, sometimes with impaired neurological development.
INVESTIGATIONS
Differentiated by specific patterns of porphyrins and porphyrin precursors, and confirmed by mutation analysis.
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