Editor—Cystic fibrosis (CF) is the most common recessive genetic disorder affecting about 1 in 2500 white live births with a carrier frequency of 1 in 25.1 The incidence of this disease has been found to be somewhat lower in Nordic countries,2 especially Finland.3 To date more than 800 mutations have been identified in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (http://www.genet.sickkids.on.ca/cftr/). The major mutation, ΔF508, accounts for 72.8% of the CF chromosomes in northern and central European countries,4 but the frequencies and types of mutations in different populations vary considerably depending on the ethnic and geographical origin of the population tested.

In our previous report, the incidence of CF was estimated to be about 1 in 4500 live births in Estonia.5 The present study was undertaken to identify the whole spectrum ofCFTR gene mutations in Estonian patients.

Thirty families with CF patients were studied. We think the patients should account for most of the CF cases in Estonia, as they attend the central hospitals, but the exact number of CF patients is not known. Diagnostic criteria were based on repeated positive sweat chloride tests (>60 mmol/l) and on typical findings of pulmonary/gastrointestinal disease. In addition, 20 more patients suspected of having CF, with either undefined pancreatitis or a broad spectrum of respiratory diseases and borderline (40-60 mmol/l/l) or normal (<40 mmol/l) sweat chloride values, were analysed for mutations in the CFTR gene.

First, several known mutations were tested directly by the heteroduplex analysis (HA; ΔF508, 394delTT, polyT variants in IVS8), restriction digestion (RD; G551D, R553X, 1811+1.6kbA→G, L206W, 3849+10kbC→T), and amplification refractory mutation system (ARMS, kits from Cellmark Diagnostics, UK; G542X, 621+1G→T, N1303K). As a result of this screening, only two mutations were found: ΔF508 was found in 31 (51.7%) alleles and …