These factors include. 1  Living at high latitudes (closer to the polar regions), particularly during winter months. 2  Air quality conditions: high levels of air pollution. 3  Weather conditions: dense cloud covering. 4  The degree to which clothing covers the skin. 5  Use of sunscreen. 6  Skin pigmentation: darker skin types.
A few cases of severe homocysteinemia have been due to rare MTHFR gene mutations (sometimes in combination with a second common MTHFR gene mutation). Symptoms in these patients varied greatly but often involved pronounced neurological symptoms and blood vessel disease.
MTHFR gene mutation is a genetic change that affects an enzyme involved in breaking down the amino acid homocysteine. About 33% of Americans have one copy of a common MTHFR gene mutation (C677T). Having one copy of C677T or one copy of another common mutation A1298C is not associated with significant health risks.