FACTOR-V-LEIDEN (ACTIVATED PROTEIN-C RESISTANCE) VERSUS FACTOR-V DEFICIENCY IN PADUA, ITALY

Ten homozygous patients with factor V deficiency and 19 homozygous pat ients with activated protein C (APC) resistance were seen in Padua dur ing the last 30 or 3 years, respectively. The actual numbers of hetero zygous patients seen during the same periods of time were 41 and 306, respectively. All patients came from the northeastern part of Italy wi th a population of 10,000,000 people. The probable prevalence of homoz ygous patients was obtained by multiplying the actual number by four. The theoretical prevalence of heterozygous patients was obtained using the formula 2 qp, where q is the frequency of the abnormal gene as ca lculated by the square root of frequency of the homozygotes and p is t he frequency of the normal allele as calculated by the formula p = (1 - q). Using such calculations, the number of heterozygotes probably ex isting in northeastern Italy is 39,840 and 56,497, respectively for th e factor V deficiency and for APC resistance. After correction for the different observation periods (3 years vs. 30 years), there are 56,49 7 per 10 million people (5.6% of the population) for factor V Leiden. The prevalence of factor V deficiency is 0.39% of the population. Ther efore the factor V Leiden mutation responsible for APC resistance appe ars to be more prevalent than factor V deficiency on the basis of actu al figures and accepted theoretical calculations.