Plasma porphyrin concentrations in porphyria cutanea tarda.

Porphyria cutanea tarda (symptomatica) (PCT) is an acquired hepatic porphyria, usually caused, in susceptible people, by liver damage from a high ethanol intake. Clinically, patients have skin fragility, hypertrichosis, photosensitivity and hyperpigmentation, and biochemically there is a high urinary excretion of uroporphyrin, hepatic siderosis, abnormal iron metabolism (Turnbull, Baker, Vernon-Roberts & Magnus, 1973) and increased hepatic 6-aminolaevulinic acid (ALA) synthetase (EC 2.3.1.13) (Dowdle, Mustard & Eales, 1967). Venesection, repeated at fortnightly intervals until mild iron-deficiency anaemia occurs, produces a clinical and biochemical remission, which is usually sustained, and is associated with suppression of hepatic ALA synthetase activity (Moore, Turnbull, Barnardo, Beattie, Magnus & Goldberg, 1972). Photosensitivity in PCT is due to raised levels of porphyrin in the skin (Magnus, 1968). As erythrocyte porphyrin levels are normal, it has been assumed that they are transported from the liver in the plasma, but direct measurements have not previously been reported. This paper deals with the measurement of these plasma porphyrin levels.