Colonic Infiltration With Chronic Myelomonocytic Leukemia

Andelka D. LoSavio; Alana P. Bunnag; David T. Rubin

Disclosures

Nat Clin Pract Gastroenterol Hepatol. 2007;4(4):229-233. 

In This Article

Differential Diagnosis

In this case, diarrhea was the clinical manifestation of leukemic gastrointestinal infiltration. There are, however, many other possible clinically important presentations. Patients with mild, nonspecific abdominal pain, indigestion, or nausea[8] have been described, as have patients with malabsorption due to protein-losing enteropathy.[9] Acute presentations include intussusception, appendicitis, necrotizing enteritis, perforation, and sepsis.[9] Multiple authors have reported anorectal manifestations including perianal ulcers, abscesses, mucosal sloughing, and severe prolapsing hemorrhoids thought to be infiltrated with leukemic cells.[10]

Inflammatory Bowel Disease

IBD comprises two major disorders: ulcerative colitis and Crohn's disease. Ulcerative colitis is characterized by inflammation of the mucosal layer of the colon, which typically begins in the rectum and potentially extends proximally. Crohn's disease is characterized by transmural inflammation that can affect any portion of the gastrointestinal tract, often in a discontinuous pattern. Diarrhea, abdominal pain, and gastrointestinal bleeding can be seen in patients with either disorder, depending on the location and extent of disease. The diagnosis is typically made based on a characteristic clinical history and typical endoscopic and pathologic findings. An association between the development of IBD and a pre-existing hematologic malignancy has been reported, however, the pathogenic relationship has not been elucidated.[11] Given her age, concomitant CMML, the absence of crypt architectural distortion on pathology specimens and the predominantly monocytic infiltrate, IBD was thought to be a less likely diagnosis in this patient.

Ischemic Colitis

Ischemic colitis is a form of mesenteric ischemia. In most cases, the vascular insult is nonocclusive in nature and most commonly affects the 'watershed' areas of the colon such as the splenic flexure and rectosigmoid junction. Ischemic colitis is characterized by mild abdominal pain, diarrhea and rectal bleeding, severe cases of ischemic colitis can progress to peritonitis and shock. The diagnosis can be made based on a patient's clinical history, abdominal imaging and endoscopy, which frequently demonstrates a segmental distribution of mucosal injury and rectal sparing. Mild to moderately severe ischemic colitis requires supportive treatment, which includes intravenous fluids, bowel rest, and antibiotics. Severe cases can require surgical exploration and colonic resection. Although ischemic colitis has been reported in the setting of hematologic malignancy, this condition has most often been described in the setting of chemotherapy or in the presence of a hypercoagulable state.[12] In this patient, diffuse mucosal injury and rectal involvement argued against ischemia as the diagnosis.

Drug-induced Diarrhea

Iatrogenesis should always be suspected in cases of acute and chronic diarrhea, especially when the initiation of a medication is temporally related to the onset of symptoms. Depending on the medication, drug-related diarrhea can be osmotic, secretory or inflammatory in nature. Levothyroxine, rabeprazole, celecoxib, and echinacea all have reported gastrointestinal toxicity with diarrhea;[13] however, only celecoxib has been linked to the development of inflammatory diarrhea in the setting of microscopic colitis.[1] In this patient, chronic use of all of the above medications argued against a drug effect as the cause of new onset diarrhea.

Infectious Diarrhea

Viral, bacterial and protozoal agents are well-known causes of acute and chronic diarrhea. Specific infectious etiologies are suspected on the basis of clinical history, travel, exposure to particular foods, recent exposure to antibiotics, and the patient's level of immune competence. Distinct histopathologic features mean that infectious enterocolitis is usually readily distinguished from IBD; however, there are several well-known infections that mimic IBD. These include (but are not limited to) shigellosis, amoebiasis, salmonellosis, yersiniosis, campylobacteriosis, tuberculosis and infections with C. difficile, cytomegalovirus, and herpes virus.[2] Stool studies and biopsy specimens in this patient revealed no evidence of acute or chronic infectious diarrhea.

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