a deficiency of this substance leads to pernicious anemia
Vitamin B12 deficiency anemia Vitamin B12 deficiency anemia, of which pernicious anemia is a type,[8] is a disease in which not enough red blood cells are present due to a lack of vitamin B12.[5] The most common initial symptom is feeling tired.[4] Other symptoms may include shortness of breath, pale skin, chest pain, numbness in the hands and feet, poor balance, a smooth red tongue, poor reflexes, depression and confusion.[4] Without treatment some of these problems may become permanent.[5]