Amyloidosis is characterized by extracellular deposition of abnormal proteins in organs, including six types: primary, secondary, hemodialysis-related, hereditary, senile, and localized [1]. Primary amyloidosis is associated with monoclonal light chains in serum and/or urine, with 15% of patients having multiple myeloma. Secondary amyloidosis is associated with inflammatory, infectious, and neoplastic diseases, and these two types of amyloidosis are the most common type in clinical practice. Generally, amyloid deposits are distributed along the gastrointestinal (GI) tract, liver, kidney, and spleen, and sometimes is associated with the onset of inflammatory bowel disease (IBD) [1]. The duodenum and stomach are the most common sites for protein deposition. GI involvement is common in cases of systemic amyloidosis, and the majority of cases of gastric amyloidosis are related to systemic involvement of amyloidosis. Nausea, vomiting, hematemesis, and epigastric pain are the symptoms, and purpura, macroglossia, joint swelling, congestive heart failure and hepatomegaly are the typical characteristics of physiological examination of systemic amyloidosis.
For localized primary amyloidosis in the GI tract, the most common location is the stomach [7], followed by the esophagus [8], small bowel [9], and colon [10]. Localized gastric amyloidosis is a rare disorder characterized by the extracellular deposition of insoluble fibrillary protein confined to the stomach [4]. The clinical presentation of localized gastric amyloidosis ranges from no symptoms to nausea, vomiting hematemesis, melena, abdominal pain, a gastric mass or tumor, inflammation, erosions, healing ulcers, and even perforation [11, 12]. Epigastric pain is one of the most common symptoms, and gastric outlet obstruction may be due to submucosal tumors [13], polyps, or antral narrowing [14]. In our study, all lesions were located in the gastric antrum, one of which spread to the whole stomach, and the gastric mucosal background displayed active gastritis. Among the 3 cases, epigastric pain was a prominent symptom, with no typical signs of systemic amyloidosis by physiological examination, strongly suggesting local gastric amyloidosis.
Conventional endoscopic findings, including thickened irregular gastric folds [15], gastric outlet obstruction [14], loss of rugal folds [1, 14], gastric ulcers with clean bases or irregular edges [14, 16, 17], arteriovenous malformations [18], granular-appearing mucosa [19], plaque-like lesions [20], ulcerative gastritis [21], submucosal tumor-like features [4], healing gastric ulcer [6] and gastroparesis [22], have been reported in gastric amyloidosis. Three cases had different lesions, including a fainted reddish flat-elevated lesion with multiple nodules on the surface; a white-yellowish circular area with the appearance of multiple nodules and active gastritis; and redness, sporadic erosion, thickened irregular gastric folds and gastric outlet obstruction. Therefore, there was no specific feature of localized primary amyloidosis during endoscopic examination under white light. With the development of endoscopic technology, NBI and ME-NBI are becoming increasingly useful in detecting early gastric cancer. Thus, it is important to exclude cancers such as undifferentiated adenocarcinoma or MALT lymphoma because localized gastric amyloidosis commonly appears as a cancerous lesion or mass. In our observations, it was difficult to distinguish MALT lymphoma by NBI and ME-NBI imaging in these cases, we observed expanded normal glands with changed polarity, mucosal irregularities, and round small vascular changes such as dilated vessels without variable caliber on the surface and tree-like vessels, which were considered characteristics of MALT lymphoma [23]. Moreover, despite the reported utility of EUS in diagnosing gastric amyloidosis [24], specific EUS features were not well defined. In our 3 cases, the EUS images of localized primary amyloidosis showed thickening of the gastric wall with homogenous lesions in the first and second layers only. Therefore, it is still difficult to distinguish gastric amyloidosis from other lesions, such as gastric cancer and MALT lymphoma, by EUS. However, it is very important for endoscopists to consider this rare disease when performing endoscopic diagnoses.
Pathological analysis is the gold standard for the diagnosis of gastric amyloidosis, and biopsy with pathology assessment and staining are very helpful for determining the correct diagnosis. In AL amyloidosis, there is greater deposition of amyloid in the muscularis mucosa, submucosa, and muscularis propria, in contrast to AA amyloidosis, which does not involve deeper layers of the gastric wall [3] but instead manifests as mucosal lesions that can be visualized by endoscopy and biopsied. Thus, it is necessary to perform a biopsy to reach the muscularis mucosa. In these 3 cases, H&E staining showed abundant amyloid deposition in the mucosal or submucosal layers. Congo red staining with the pretreatment of potassium permanganate confirmed the light chain AL type, which was reconfirmed by polarized light microscopy with the observation of apple-green birefringence in the lesions. Additionally, serum and urine immunoelectrophoresis showed no monoclonal immunoglobulin or free light chain. k and l light chains in serum or urine were all in the normal range. These are the typical pathological findings for primary amyloidosis.
For patients with a diagnosis of amyloidosis, it is important to determine whether they have systemic or localized disease because the treatment and prognosis are different for each disease entity. For instance, treatment for systemic AL amyloidosis is chemotherapy and stem cell transplantation [1], but localized GI amyloidosis without evidence of systemic involvement has an excellent prognosis.
From our experience, in the first case, because the lesion was less than 2 cm, ESD was recommended for not only the diagnosis but also treatment and resulted in a good prognosis and minimal recovery time. This kind of treatment is also recommended when mucosal biopsies are negative [6]. For the second case, because a circular area in the gastric antrum and the patient had no gastric outlet obstruction due to narrowing of the antrum, we performed Hp eradication to reduce her pain, which was successful. She was followed up for 4 years, and there were no changes in the relevant lesions. However, at this stage, in addition to close follow-up, no other good treatment was recommended. These clinical observations suggested that patients with localized primary amyloidosis should be monitored and treated symptomatically because they rarely experience progression to systemic disease, and their survival is excellent. The outcome of the third case was unfortunate; due to late detection, amyloidosis was deposited in the whole stomach, particularly in the gastric antrum, resulting in low gastric motility, obstruction and gastric retention. Time for effective treatment was lost.