Can anyone explain what a1298c homozygous genetic mutation could cause?

MTHFR mutation. The genetic finding can possibly increase clotting problems. The mthfr protein is responsible for metabolism of homocysteine. High homocysteine levels can aggravate vessel walls causing a higher risk of clotting. The high homocysteine levels can be treated with folate (folic acid) supplementation, which should decrease the risk.
See below. Mthfr 1298 is not associated with higher homocysteine. That is what the 677 does. 1298 can have: • increased ammonia level • decreased Dopamine & serotonin • decreased epi and norepi • decreased nitric oxide • increased blood pressuremuscle tenderness • prone to bh4 shortage. • may benefit from lower protein diet as ammonia depletes bh4.