ERYTHROPOIETIC PROTOPORPHYRIA: A RAPID METHOD TO DETECT ASYMPTOMATIC GENE CARRIERS

As it always happens for different forms of porphyria, many individuals who inherit the gene mutation responsible for erythropoietic protoporphyria (EPP) remain asymptomatic (latent) throughout life. Nevertheless in some circumstances identification of asymptomatic EPP gene carriers could play an important role in the knowledge of this disease: through an extremely simple method - given the availability of a spectrofluorometer - it is possible to evaluate accurately the EPP prevalence in large populations. We studied: 14 EPP individuals (8 unrelated EPP patients and 3 couples of EPP siblings); 8 asymptomatic relatives from three unrelated families affected by EPP; a control group of 10 subjects. Fluorescence emission spectroscopy of red blood cell was carried out as described by Poh-Fitzpatrich with minor modifications. RBC from EDTA anticoagulated blood were scanned between 570 and 750 nm at an excitation wavelength of 405 in a Perkin-Elmer LS55 luminescence Spectrometer. Fourteen EPP patients were uniformly found, as already described by Poh-Fitzpatrich, to have a distinctive erythrocytes porphyrin fluorescence wavelength maximum at 626 (± 1) nm. Six out of the 8 asymptomatic relatives showed an evident peak at 626 nm even if the fluorescence intensity of this peak was at least 5 times minor then that identifiable in RBC of EPP patients. Scans from 10 normal subjects showed no peak or a very small peak with a maximum emission of 619 nm or less. All 8 asymptomatic relatives underwent genetic analyses to identify specific familial mutations. The genetic investigation confirmed biochemical data.