POPULATION DIFFERENCES IN THE FREQUENCY OF THE FACTOR-V LEIDEN VARIANT AMONG PEOPLE WITH CLINICALLY SYMPTOMATIC PROTEIN-C DEFICIENCY

The factor V Leiden variant, responsible for the phenomenon of activat ed protein C resistance, was found to be less frequent among British ( 0.06) and Swedish/Danish (0.15) protein C deficiency patients than pre viously reported in a Dutch study (0.19). In the Swedish population, a significantly increased frequency of the factor V Leiden allele was a pparent in protein C deficiency patients as compared to healthy contro ls. However, this was not found in the British population. Coinheritan ce of the factor V Leiden variant is therefore unlikely to be the sole determinant of whether a person with protein C deficiency will come t o clinical attention. Nevertheless, when patient data were analysed by type of protein C deficiency, it was noted that the frequency of the factor V Leiden variant was 2.8-fold higher in type II patients compar ed to type I patients. A possible explanation of this disparity is dis cussed.