Under the Microscope: How would you diagnose this case?

An 18 year-old woman presented with abdominal pain and hematemesis. At endoscopy, there were small nodules in the gastric antrum without ulceration. The duodenum initially appeared normal, but contact with the endoscope demonstrated mucosal friability. Below are representative photomicrographs of the duodenum and stomach biopsies (Figures 1 and 2). What is your diagnosis?

a) Helicobacter Gastritis. d) Amyloidosis.
b) Collagenous Gastroenteritis. e) Reactive Gastropathy.
c) Gastric Antral Vascular Ectasia (GAVE).

Amyloidosis is a condition in which characteristic proteins that adversely affect normal physiology are deposited in tissues. Amyloid protein undergoes abnormal post-translational modifications that prevent proteolysis, leading to accumulation of the insoluble proteins in tissue. Over time, this accumulation may lead to compromise of the normal function of the tissue or organ involved.

Amyloidosis may be inherited or acquired. More than 50 amyloid proteins have been identified, most of which are associated with disease. 1 Amyloidosis may be localized, as with Senile Amyloid of cardiac atria (AANF) and Alzheimer’s disease (Aβ), or systemic, such as Serum Amyloid A disease (AA) and Amyloid light-chain disease (AL). Amyloidosis may also be classified as a primary disease, as in multiple myeloma (AL), or secondary, occurring as a complication of a chronic inflammatory disease.

Many types of amyloid have been found to involve the GI tract, including the most commonly occurring amyloid types AA and AL. Lesser known amyloid types have also been found in GI specimens, such as Aβ (β protein precursor), AApoA 1 (apolipoprotein A1), Alys (lysozyme), Acys (cystatin C), and Agel (gelsolin). 2 In many cases of systemic amyloidosis, the GI tract may be involved without clinical symptoms. When GI tract involvement by amyloidosis does become clinically apparent, it may manifest as bleeding, pseudoobstruction, dysmotility, or even volvulus. Endoscopic findings may include nodules, friable mucosa, areas of ischemia, and ulcers. 3

When amyloid involves the GI mucosa it is identified microscopically as extracellular deposits of eosinophilic amorphous material. This pink material may also be seen within the small vessels and the muscular layers of the gut. The most specific special stain to confirm the presence of amyloid is the Congo red stain. With a Congo red stain, amyloid is pink under white light (figure 3) and shows apple-green birefringence under polarized light (figure 4).4 If desired, the specific subtype of amyloid can be determined from routine biopsy material by a special technique that utilizes laser microdissection and mass spectrometry. 5
– Eric Naar, MD, GI pathologist

References
1. Feldman,M,etal.SleisengerandFordtran’sGastrointestinalandLiverDisease.2006. Saunders Elsevier. 735-9.
2. Lewin,D.OdzeandGoldblum’sSurgicalPathologyoftheGITract,Liver,BiliaryTract,and Pancreas. 2009. Saunders Elsevier. 116-7.
3. Ebert, EC and Nagar, M. Gastrointestinal manifestations of amyloidosis. 2008. Am J Gastroenterol 103(3): 776-87.
4. Vowles,GH,andRJFrancis.BandroftandGamble’sTheoryandPracticeofHistological Techniques. Churchill Livingstone. 303-20.
5. Vrana, JA, Gamez, JD, Madden, BJ, et al. Classification of amyloidosis by laser microdissection and mass spectromerty-based proteomic analysis in clinical biopsy specimens. 2009. Blood 114: 4957-59.

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