In your case, chances of autoimmune disease are more as other blood
tests are normal. The only other finding is low
folate. Low levels
can be due poor intake of folic acid rich food (green leafy vegetables, yellow fruits, avocado, beans, lentils, cauliflower etc) or due to malabsorption syndromes (IBS, tropical sprue, Crohn’s, celiac etc) or due to eating disorders causing malnutrition.
Since a confirmed diagnosis cannot be given on net please consult your doctor regarding this.