Thrombosis risk in carriers of the factor V Leiden mutation: is it associated with a defined skin color?

Factor V Leiden (FVL; G1691A) is an autosomal dominant mutation with a high risk for thrombosis. Speculation that founders of FVL lived in the Middle East is supported by a prevalence of FVL that is higher in Arabs residing in Israel, Jordan, Lebanon, and Syria (12-14%) than in other white populations like Europeans (4-5%, up to 15% in the South of Sweden). We sought to verify the appropriate use of skin color as a clinical sign by which Arab individuals in Kuwait are included or excluded from testing for FVL. After institutional approval, 200 healthy Arabs residing in Kuwait consented to participate. Skin type was distinguished for the participants by Fitzpatrick natural skin color classification: 76 (38%) skin type II (white), 96 (48%) Mediterranean skin type IV (brown), and 28 (14%) skin type VI (black). FVL was tested by real-time PCR, and the percentage of carriers was calculated in each group. FVL was positive in 17 (8.5%) of the total subjects: 8 (10.5%) skin type II, 7 (7.3%) skin type IV, and 2 (7.1%) skin type VI. Therefore, FVL shows an even distribution in Arabs, and all Arabs residing in Kuwait should be tested for FVL irrespective of skin color.