Porphyrias in Norway.

BACKGROUND Porphyria is an umbrella term for a group of largely hereditary diseases that are due to defective haem synthesis. The diseases have a varied and partly overlapping range of symptoms and presentations. The commonest forms of porphyria are porphyria cutanea tarda, acute intermittent porphyria and erythropoietic protoporphyria. The purpose of this study is to provide an overview of the prevalence and pathological manifestations of porphyrias in Norway. MATERIAL AND METHOD Information on all patients registered with the Norwegian Porphyria Centre (NAPOS) up to 2012 was used to estimate the prevalence and incidence of porphyrias in Norway. Figures on symptoms, precipitating factors and follow-up routines were obtained from the Norwegian Porphyria Registry, which includes 70% of Norwegians registered with NAPOS as having porphyria. RESULTS The prevalence of porphyria cutanea tarda was approximately 10 : 100,000 and that of acute intermittent porphyria approximately 4 : 100,000. The total incidence of all porphyrias was approximately 0.5-1 : 100,000 per year. Diagnostic delay, i.e. the time passing between the onset of symptoms and diagnosis, varied from 1-17 years depending on the type of porphyria. There was wide variation in the frequency with which patients with the various types of porphyria went for medical check-ups. INTERPRETATION The prevalence of acute intermittent porphyria and porphyria cutanea tarda appears to be higher in Norway than in most other countries. Data from the Norwegian Porphyria Registry makes it possible to demonstrate differences in treatment and follow-up of porphyria patients and may be used to initiate necessary measures.