S1971 Waldenstrom Macroglobulinemia: A Malignant Mimicker of IBD

Abstract

Introduction: Waldenstrom macroglobulinemia (WM) is a lymphoplasmacytic lymphoma in the bone marrow with IgM gammopathy in the blood. Annually ∼1400 cases are diagnosed in the US, with typical presentation of B symptoms, fatigue, neuropathy, and mucosal bleeding. Only 3% of patients present with colonic symptoms. We describe a case of WM with rectal involvement presenting as bloody diarrhea, mimicking inflammatory bowel disease (IBD). Case Description/Methods: A 56-year-old man with depression, anxiety, and fibromyalgia presented with 6 months of diarrhea with mucous and rectal bleeding. He underwent upper endoscopy and colonoscopy with Helicobacter pylori gastritis, proctitis, and inflammatory polyps. He symptoms worsened despite rectal mesalamine, including weight loss and night sweats. Budesonide oral and foam resolved the bleeding but diarrhea continued despite rifaximin. Around this time, he was thought to have irritable bowel syndrome. Two years later, he had recurrence of daily bowel movements with mucous and rectal bleeding, plus fecal incontinence, tenesmus, and rectal and abdominal pain. He also noticed myalgias, arthralgias, parasthesias, fatigue, and chills. Rheumatology suggested fibromyalgia as the culprit, in part due to elevated ESR. After his GI symptoms renewed suspicion for IBD, repeat colonoscopy showed a 3 cm rectal mass with ulcer and stenosis at the recto-sigmoid colon. Biopsies showed eosinophilic proteinaceous material positive for PAS-D, negative for fibrosis and amyloid and concerning for malignancy. EUS confirmed inflammatory polyps and rectal thickness ( Figure 1). Hematology performed immunofixation with faint monoclonal IgM-lambda, and bone marrow biopsy confirmed lymphoplasmacytic lymphoma concerning for WM. Discussion: WM rarely involves the GI tract, with fewer colonic and rectal presentations than small bowel. The IgM deposition can cause severe malabsorption, steatorrhea, obstructive symptoms, or GI bleeding. Especially in cases of bloody stools and localized colonic thickening, WM can be mistaken for IBD. In our case, factors more suggestive of WM included degree of colonic thickening and pathologic PAS-D positivity. Particularly, raised lesions should prompt investigation for malignant processes, despite surrounding inflammatory changes. Diagnosis of WM usually involves multiple specialists and procedures such as bone marrow biopsy. WM treatment includes bruton tyrosine kinase inhibitors or bendamustine with rituximab, the latter of which improved our patient’s GI symptoms.Figure 1.: Image 1. Colonoscopy and lower endoscopic ultrasound (EUS) visualized circumferential wall thickening and stenosis in rectum, with polyps and stenosis in sigmoid colon. a. During colonoscopy, a benign-appearing, intrinsic moderate stenosis measuring 4 cm in length was found in the recto-sigmoid colon, due to circumferentially congested edematous polypoid mucosa with overlying exudate. b. Several 10 to 16 mm sessile polyps were seen with inflammatory appearance in the sigmoid colon. c-d. During EUS, circumferential wall thickening was found in the rectum at the superficial and deep mucosa. There was no evidence of an infiltrative subepithelial mass. The muscularis propria layer was normal throughout.