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1. Pathophysiology of pernicious anemia :-

In pernicious anemia vitamin B12 is unavailable owing to a lack of intrinsic factor, a substance responsible for intestinal absorption of the vitamin. In a healthy person, intrinsic factor is produced by the parietal cells of the stomach, the cells that also secrete hydrochloric acid. Intrinsic factor forms a complex with dietary vitamin B12 in the stomach. The complex remains intact, preventing degradation of the vitamin by intestinal juices, until it reaches the ileum of the small intestine, where the vitamin is released and absorbed into the body .

When intrinsic factor is prevented from binding with vitamin B12 or when the parietal cells are unable to produce intrinsic factor, the vitamin is not absorbed and pernicious anemia results. This effect is thought to stem from an autoimmune reaction in which the malfunctioning immune system produces antibodies against intrinsic factor and against the parietal cells.

Without an adequate amount of vitamin B12, the body is unable to synthesize DNA properly. This in turn affects red blood cell production: the cells divide, but their nuclei remain immature. These cells, called megaloblasts, are for the most part destroyed in the bone marrow and are not released to the circulation. Some megaloblasts mature to become large red blood cells called macrocytes; they reach the circulation but function abnormally. A deficiency of white blood cells (leukopenia) and platelets (thrombocytopenia) in the blood may occur.

Manifestation listed above related to pernicious anemia are :-

- sore, swollen tongue

- tingling feeling in his toes

- vomiting

- diarrhea

2. - Intestinal problems or other medical conditions that interfere with absorption of vitamins. Abnormal bacterial growth in your stomach or surgery to your intestines or stomach can interfere with the absorption of vitamin B-12.

- Lack of intrinsic factor. Most people with a vitamin B-12 deficiency anemia lack intrinsic factor — a protein secreted by the stomach that is necessary for absorption of vitamin B-12. Lack of intrinsic factor may be due to an autoimmune reaction, or it may be inherited.

- Helicobacter pyroli infection

3. Complications of pernicious anemia are :-

- gastric cancer

- nerve damage

- digestive tract problem

- heart damage

- memory problems , confusion ,and other neurological symptoms

4. The diagnostic methods to diagnose pernicious anemia are :-

- Complete blood count. This test measures vitamin B-12 and iron levels in blood serum.

- Vitamin B-12 deficiency test: Your doctor can assess your vitamin B-12 levels through a blood test. Low levels indicate a deficiency.

- Biopsy. Your doctor may also want to see if there has been any damage to your stomach walls. They can diagnose this through a biopsy. The biopsy involves removing a sample of the stomach’s cells. The cells are then examined microscopically for any damage.

- IF deficiency test. Intrinsic factor deficiency is tested through a blood sample. The blood is tested for antibodies against IF and the stomach’s cells.