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.
I have been diagnosed with the heterogenous MTHFR gene mutation. My Dr. started supplementing me with methylcobalamine (5,000) tablet that also had folic acid in it. For the first couple of months I had no side effects but then I started getting gastrointestinal symptoms so I cut out then eliminated the B12.