Autoimmune gastritis is a chronic condition where the body’s immune system mistakenly attacks healthy cells in the stomach lining, specifically the parietal cells. This attack leads to inflammation and gradual destruction of these cells, which produce gastric acid and intrinsic factor. The damage impairs nutrient absorption, such as vitamin B12 and iron, potentially leading to deficiencies.
Initial Clues and Assessment
Patients often seek medical attention for subtle, non-specific symptoms that develop slowly over time. These can include persistent fatigue, weakness, light-headedness, or heart palpitations, often linked to anemia. Digestive discomfort, such as nausea, vomiting, or a feeling of fullness after eating small amounts, may also be present.
Upon presentation of these symptoms, a doctor takes a comprehensive medical history, inquiring about personal health issues, family history of autoimmune conditions, and lifestyle factors. A physical examination follows, where the doctor looks for signs like pallor, indicating anemia, or a rapid pulse. A sore tongue, known as glossitis, might also be observed, which is a symptom of vitamin B12 deficiency.
Key Blood Tests
Specific blood tests are a common initial step in diagnosing autoimmune gastritis. A complete blood count (CBC) is routinely performed to check for anemia, particularly macrocytic anemia (larger-than-normal red blood cells). This type of anemia often results from vitamin B12 deficiency, a direct consequence of parietal cell destruction and impaired intrinsic factor production.
Measuring vitamin B12 levels directly in the blood helps confirm a deficiency, a common finding in autoimmune gastritis. Beyond general nutrient levels, specific autoantibodies provide strong evidence for the autoimmune nature of the condition. Parietal cell antibodies (PCA) are present in most patients with autoimmune gastritis, sometimes even before overt symptoms appear.
Intrinsic factor antibodies (IFA) are another specific marker, though less sensitive than PCA. These antibodies target intrinsic factor, a protein produced by parietal cells necessary for vitamin B12 absorption. Elevated serum gastrin levels, known as hypergastrinemia, can also suggest autoimmune gastritis, as the stomach attempts to compensate for reduced acid production by increasing gastrin secretion.
Endoscopy and Biopsy
Following initial blood tests, an endoscopy with biopsy is often performed to confirm the diagnosis and assess the extent of stomach damage. During this procedure, a thin, flexible tube with a camera is gently inserted through the mouth, allowing visualization of the esophagus, stomach, and the beginning of the small intestine. While conventional endoscopy might not always show obvious changes, more advanced techniques can reveal subtle mucosal alterations.
Tissue samples, or biopsies, are taken from specific areas of the stomach, particularly the body and fundus, where parietal cells are located. These samples are then examined by a pathologist under a microscope. Pathologists look for characteristic findings, such as glandular atrophy (loss of gastric glands). They may also observe metaplasia, where stomach lining cells are replaced by other cell types, such as intestinal metaplasia or pseudopyloric metaplasia. The presence of inflammatory cells, including lymphocytes, plasma cells, and granulocytes, infiltrating the stomach lining is another indicator.
Confirming the Diagnosis
Diagnosing autoimmune gastritis involves carefully evaluating all available information, as no single test is sufficient on its own. A comprehensive assessment considers the patient’s reported symptoms and findings from the physical examination. Blood test abnormalities, such as anemia, low vitamin B12 levels, specific autoantibodies like PCA and IFA, and elevated gastrin, all contribute to the diagnostic picture.
The characteristic changes observed in the stomach biopsy, including glandular atrophy, metaplasia, and inflammation, provide definitive microscopic evidence of the disease. By integrating these diverse pieces of evidence—clinical presentation, laboratory results, and histological findings—healthcare providers can arrive at a definitive diagnosis of autoimmune gastritis. This comprehensive approach also helps differentiate it from other forms of gastritis or conditions that may present with similar symptoms.