Atrophic gastritis in the context of Iron deficiency anaemia

Helicobacter pylori, previously known as Campylobacter pylori, is a gram-negative, flagellated, helical bacterium. Mutants can have a rod or curved rod shape that exhibits less virulence. Its helical body (from which the genus name Helicobacter derives) is thought to have evolved to penetrate the mucous lining of the stomach, helped by its flagella, and thereby establish infection. While many earlier reports of an association between bacteria and the ulcers had existed, such as the works of John Lykoudis, it was only in 1983 when the bacterium was formally described for the first time in the English-language Western literature as the causal agent of gastric ulcers by Australian physician-scientists Barry Marshall and Robin Warren. In 2005, the pair was awarded the Nobel Prize in Physiology or Medicine for their discovery.

Infection of the stomach with H. pylori does not necessarily cause illness: over half of the global population is infected, but most individuals are asymptomatic. Persistent colonization with more virulent strains can induce a number of gastric and non-gastric disorders. Gastric disorders due to infection begin with gastritis, or inflammation of the stomach lining. When infection is persistent, the prolonged inflammation will become chronic gastritis. Initially, this will be non-atrophic gastritis, but the damage caused to the stomach lining can bring about the development of atrophic gastritis and ulcers within the stomach itself or the duodenum (the nearest part of the intestine). At this stage, the risk of developing gastric cancer is high. However, the development of a duodenal ulcer confers a comparatively lower risk of cancer. Helicobacter pylori are class 1 carcinogenic bacteria, and potential cancers include gastric MALT lymphoma and gastric cancer. Infection with H. pylori is responsible for an estimated 89% of all gastric cancers and is linked to the development of 5.5% of all cases cancers worldwide. H. pylori is the only bacterium known to cause cancer.

Vitamin B₁₂ deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B₁₂. Symptoms can vary from none to severe. Mild deficiency may have few or absent symptoms. In moderate deficiency, feeling tired, headaches, soreness of the tongue, mouth ulcers, breathlessness, feeling faint, rapid heartbeat, low blood pressure, pallor, hair loss, decreased ability to think and severe joint pain and the beginning of neurological symptoms, including abnormal sensations such as pins and needles, numbness and tinnitus may occur. Severe deficiency may include symptoms of reduced heart function as well as more severe neurological symptoms, including changes in reflexes, poor muscle function, memory problems, blurred vision, irritability, ataxia, decreased smell and taste, decreased level of consciousness, depression, anxiety, guilt and psychosis. If left untreated, some of these changes can become permanent. Temporary infertility, reversible with treatment, may occur. A late finding type of anemia known as megaloblastic anemia is often but not always present. In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement.

Causes are usually related to conditions that give rise to malabsorption of vitamin B₁₂ particularly autoimmune gastritis in pernicious anemia. Other conditions giving rise to malabsorption include surgical removal of the stomach, chronic inflammation of the pancreas, intestinal parasites, certain medications such as long-term use of proton pump inhibitors, H2-receptor blockers, and metformin, and some genetic disorders.

Gastritis is the inflammation of the lining of the stomach. It may occur as a short episode or have a long duration. There may be no symptoms, but the most common symptom is upper abdominal pain. Other symptoms include nausea and vomiting, bloating, indigestion, loss of appetite and heartburn. Complications may include stomach bleeding, stomach ulcers, and stomach tumors. Autoimmune atrophic gastritis may lead to issues including pernicious anemia.

Common causes include infection with Helicobacter pylori and use of nonsteroidal anti-inflammatory drugs (NSAIDs). Other causes include alcohol, smoking, cocaine, severe illness, autoimmune problems, radiation therapy and Crohn's disease. Endoscopy, a type of X-ray known as an upper gastrointestinal series, blood tests, and stool tests may help with diagnosis. Other conditions with similar symptoms include inflammation of the pancreas, gallbladder problems, and peptic ulcer disease.