Differential Diagnosis
- Single most likely diagnosis
- Pernicious anemia: This is the most likely diagnosis given the patient's low iron, low iron saturation, and positive parietal cell antibody test. Pernicious anemia is an autoimmune disorder that leads to the destruction of parietal cells in the stomach, which are responsible for producing intrinsic factor, a protein necessary for vitamin B12 absorption. The positive parietal cell antibody test supports this diagnosis, and the negative intrinsic factor antibody test does not rule it out, as not all patients with pernicious anemia will have a positive intrinsic factor antibody test.
- Other Likely diagnoses
- Iron deficiency anemia due to chronic disease: This diagnosis is possible given the patient's low iron and low iron saturation. Chronic diseases such as rheumatoid arthritis, chronic kidney disease, or chronic infections can lead to iron deficiency anemia.
- Atrophic gastritis: This condition is characterized by inflammation of the stomach lining, which can lead to the destruction of parietal cells and subsequent vitamin B12 deficiency. The positive parietal cell antibody test supports this diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Gastric cancer: Although less likely, gastric cancer can cause iron deficiency anemia and vitamin B12 deficiency. It is essential to rule out this diagnosis, especially in older adults or those with a family history of gastric cancer.
- Celiac disease: This autoimmune disorder can lead to malabsorption of iron and vitamin B12, causing deficiency. Although less likely, celiac disease can have severe consequences if left untreated.
- Rare diagnoses
- Autoimmune hemolytic anemia: This rare condition is characterized by the immune system attacking and destroying red blood cells, leading to anemia. Although unlikely, it is essential to consider this diagnosis in patients with unexplained anemia.
- Rare genetic disorders: Certain genetic disorders, such as hereditary ataxia or Imerslund-Gräsbeck syndrome, can cause vitamin B12 deficiency and iron deficiency anemia. These diagnoses are rare but should be considered in patients with unexplained anemia and a positive family history.