An Unusual Case of Small Intestine Amyloidosis

Abstract

Amyloidosis is a disorder characterized by extracellular deposition of protein fibrils in various organs. The several types of amyloidosis are defined by different precursor proteins. Amyloidosis can be classified as primary, secondary, hemodialysis-related, hereditary, senile or localized. Although amyloidosis in the gastrointestinal tract is not uncommon, it is difficult to diagnose due to the inconsistent clinical features and endoscopic findings. We present a case of small bowel amyloidosis in a patient presenting with intermittent nausea, vomiting, diarrhea and weight loss. A 72 year old male with past medical history of colon cancer (T3N1) status post sigmoidectomy and chemotherapy presented with six month history of intermittent nausea, vomiting, diarrhea and a 30 pound weight loss. He was admitted to Dartmouth-Hitchcock Medical Center and was found to have anemia, acute kidney injury with electrolyte disturbances and hypoalbuminemia. For his diarrhea, workup including stool studies was all negative. CT scan of abdomen and pelvis showed partial small bowel obstruction. A small bowel follow through demonstrated a filling defect in a mid-abdominal loop highly suspicious for an intra-luminal mass (Figure 1).Figure 1The patient underwent exploratory laparotomy with lysis of adhesions and was found to have thickened proximal bowel with enlarged lymph nodes in mesentery. The segment of small bowel was resected and opened to reveal small ulcerations and a submucosal mass. Pathology revealed extensive submucosal including foreign body type giant cell reaction to amyloid (Figure 2) and congo red stain confirmed the presence of amyloid AL- kappa light chains (Figure 3).Figure 2Figure 3He subsequently underwent bone marrow biopsy which showed a mildly increased plasma cell population (< 10%) with slight kappa light chain excess but without unequivocal demonstration of monoclonality, consistent with monoclonal gammopathy of undetermined significance (MGUS). Since he had no evidence of other organ involvement and his symptoms resolved after resection of segmental small bowel, he opted for watchful waiting rather than treatment with high dose chemo (Melphalan/Dexamethasone) with autologous stem cell transplant. The small intestine is the most common site for amyloid deposition with 3% of patients noted to have deposition on autopsy. Clinically, patient with amyloidosis of the small intestine present with diarrhea, steatorrhea, protein loss, GI bleeding, perforation, diarrhea or intussusception. Small intestine amyloidosis can be difficult to diagnose due to the low incidence rate and non-specific symptoms therefore, there needs to be a high index of suspicion in order to avoid delaying diagnosis. Amyloidosis should be considered in non-diabetic patient with nephrotic-range proteinuria, cardiomyopathy, hepatomegaly or any GI symptoms.