Fundic gland polyposis

# Overview
Fundic gland polyposis is a medical syndrome where the fundus of the stomach develops many polyps.  The condition has been described both in patients with polyposis conditions of the colon (including familial adenomatous polyposis), and in patients in whom it occurs sporadically.

# Clinical presentation
Most patients with fundic gland polyposis do not have any symptoms, and the diagnosis is made on gastroscopy done for other reasons.  Retrospective analysis of patients with sporadic fundic gland polyposis shows that a high percentage do have symptoms, but that this is more likely to be related to the underlying disease responsible for the polyposis .  These symptoms include:
- epigastric pain
- nausea
- vomiting
- weight loss
The polyps on endoscopy are usually tiny, numerous and sessile, and usually scattered throughout the fundus of the stomach, where parietal cells are more numerous.  They have the same colour as the gastric mucosa, and never have a stalk .  When the polyps are biopsied, the pathology typically shows shortened gastric pits, and both superficial and deep cystic lesions in the fundic glands.  Foci of dysplasia can sometimes be seen.

# Epidemiology and disease associations
Fundic gland polyposis is found in 0.8 to 1.9% of patients who undergo esophagogastroduodenoscopy, and are more common in middle aged women.
The most important consideration in evaluating patients with fundic gland polyposis is determining whether there is an underlying congenital cause for the condition, or whether the condition was acquired.  This is to ascertain the risk of development of gastric cancer, and to ascertain the risk of concomitant colon cancer.
Fundic gland polyposis can be found in association with the following congenital conditions :
- familial adenomatous polyposis
- attenuated familial adenomatous polyposis syndromes
- Peutz-Jeghers syndrome
- Cowden's syndrome
- juvenile polyposis
The following are acquired causes for fundic gland polyposis :
- chronic use of proton pump inhibitors
- Zollinger-Ellison syndrome
- atrophic gastritis
Helicobacter pylori infection does not correlate with fundic gland polyposis, and may cause polyp regression.

# Pathophysiology
The development of polyps depends on the underlying disorder.
In sporadic cases of fundic gland polyposis, there is usually a driving force for parietal cell hypertrophy; for example in chronic proton pump inhibitor use, the cause is up-regulation of gastrin from acid suppression.  Mutations in the -catenin gene are associated as a risk for polyp development 
In familial adenomatous polyposis, the abnormality is a mutation in the APC gene, resulting in its inactivity.  Attenuated FAP can occur from other mutations in the APC gene, and causes a phenotype wherein colonic polyps may be few in number 
Both the -catenin gene and the APC gene are involved in the same cell growth signalling pathway, but the APC gene is known to have a significantly higher association with the development of colorectal tumors .

# Cancer risk and the need for screening
There is a risk of development of cancer with fundic gland polyposis , but it varies based on the underlying cause of the polyposis.  The risk is highest with congenital polyposis syndromes, and is lowest in acquired causes.  As a result, it is recommend that patients with multiple fundic polyps have a colonoscopy to evaluate the colon .  If there are polyps seen on colonoscopy, genetic testing and testing of family members is recommended .
It is still unclear which patients would benefit with surveillance gastroscopy, but most physicians recommend endoscopy every one to three years to survey polyps for dysplasia or cancer .  In the event of high grade dysplasia, polypectomy, which is done through the endoscopy, or partial gastrectomy may be recommended.  One study showed the benefit of NSAID therapy in regression of gastric polyps, but the efficacy of this strategy (given the side effects of NSAIDs) is still spurious .