Abstract
Gastrointestinal amyloidosis (GIA), a protein deposition disorder, represents a complex common pathway that encompasses multiple etiologies and presentations. It represents a significant diagnostic and treatment challenge. The disease results from the deposition of insoluble extracellular protein fragments that have been rendered resistant to digestion. GIA can be acquired or genetic, and most commonly results from chronic inflammatory disorders (AA amyloidosis), hematologic malignancy (AL amyloidosis), and end-stage renal disease (Beta-2 amyloidosis). The deposition of these abnormal proteins interferes with gastrointestinal tract (GI) organ structure and function, most notably in the liver and small bowel. Presentation from GI involvement includes cirrhotic sequelae, abdominal pain, malabsorption, and GI bleeding. Diagnosis hinges on pathologic examination of affected tissue, with classic green birefringence under polarized light. Abdominal fat pad and rectal mucosal biopsy have been described as sites of higher sensitivity for diagnosis. Serum amyloid P scintigraphy is near 90% sensitive for diagnosis of AA amyloidosis. Patients should be considered for further evaluation to rule out additional organ involvement, notably cardiac and renal. Treatment hinges on an adequate suppression of the predisposing inflammatory disorder, or malignancy, followed by supportive therapy. Prognosis varies depending on the etiology of the disease, with the AL subtype showing worse outcomes, as well as those with hepatic involvement.
Highlights
BackgroundGastrointestinal amyloidosis, a protein deposition disorder is a complex and diverse entity with multiple etiologies and presentations
We aim to describe the current understanding of pathophysiology, epidemiology, clinical presentation, diagnosis, workup, treatment, and prognosis of gastrointestinal amyloidosis
Whole-body 123I-labeled serum amyloid P (SAP) scintigraphy is up to 90% sensitive for diagnosis of systemic a chronic inflammatory state (AA) amyloidosis and can reveal the degree of organ involvement, though cardiac involvement cannot be determined by this method [24]
Summary
Gastrointestinal amyloidosis, a protein deposition disorder is a complex and diverse entity with multiple etiologies and presentations. If systemic amyloidosis is suspected or confirmed, patients should undergo screening for bone marrow malignancy, cardiomyopathy, and nephropathy [23, 25] Those presenting with GI manifestations often have indications for endoscopy such as weight loss, dyspepsia refractory to medical therapy or GI bleeding [26,27]. The presence of hepatic amyloid deposits in this cohort portended adjusted relative risk of death of 1.98 [12] In those with AA amyloidosis where effective treatment hinges on addressing the underlying inflammatory or infectious disorder, tracking the deposition of amyloid using whole-body 123Ilabeled serum amyloid P component (SAP) scintigraphy could prove useful. The demonstration of regressing deposits via this method was associated with a 0.15 relative risk (RR) of mortality [12]
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