R.Kauppinen, Kaisa Timonen
Research Program in Molecular Medicine, Biomedicum-Helsinki, and Departments of Medicine and Dermatology, University of Helsinki, Finland
Currently 36 patients from 15 families with erythropoietic protoporphyria have been identified in Finland. Most of the patients have been children diagnosed usually at the five years of age. The majority of them have been sporadic cases appearing throughout the country. 30% (n=11) of the patients were symptom-free, 70% (n=25) experience photosensitivity and 14% (n=5) severely. None of our patients have experienced fatal liver failure although elevated transaminases (ALT:AST 2:1) have occurred especially during puberty. When currently 10 mutations in the ferrochelatase gene has been identified among Finnish EPP patients, new asymptomatic patients have been identified. However, all symptomatic EPP patients have been diagnosed using biochemical analyses such as measuring blood protoporphyrin concentration (more than 10 fold) and positive plasma fluorescence spectrum. In some cases despite a gene defect and low FECH activity, only a mild increase in blood protoporphyrin levels (up to 3-fold increase) is not sufficient for the diagnosis of symptomatic EPP, but should alert a doctor to look for other causes of photosensitivity. Of the polymorphisms in the ferrochelatase gene, -23T in intron 1 (symptomatic patients 0.70 vs symptom-free 0.70 vs healthy controls 0.30) and -48C in intron 3 (symptomatic patients 0.70 vs symptom-free patients 0.22 vs healthy control 0.07) were common among symptomatic patients. The novel mutation identified in a EPP family was IVS4+1 G-A causing a splicing defect.