Microscopic Colitis: Not Just a Disease of the Elderly

Abstract

Patient is an 18 y/o African American female with a past medical history significant for autoimmune lymphoproliferative disorder (ALPS) who was referred to the ER from clinic with 4-5 days of nausea, vomiting, diarrhea, crampy abdominal pain, and laboratory evidence of hypokalemia and metabolic acidosis. She stated that she had been having diarrhea for 3-4 months prior to presentation with intermittent episodes of constipation. Her diarrhea was associated with crampy abdominal pain that was relieved with defecation. She experienced nocturnal bowel movements with stool incontinence. She denied any fevers, chills, dark stools, or bright red blood per rectum. Physical exam was unremarkable. After an initial negative work-up for an infectious etiology, a colonoscopy and EGD were performed that showed normal endoscopic appearance of her stomach, duodenum, and colon. With no definitive cause for her symptoms, she was started empirically on a ten day course of Rifaximin to treat small intestinal bacterial overgrowth. Final pathologic results from colonic biopsy subsequently revealed evidence of lymphocytic colitis (LC). She was started on budesonide and experienced marked improvement of her symptoms. Microscopic colitis (MC) is a chronic inflammatory bowel disease that presents with chronic non-bloody diarrhea, crampy abdominal pain, and characteristic histopathologic features. It has emerged as a common etiology to aforementioned symptoms over the past decade. Ten to twenty percent of patients with chronic diarrhea are eventually diagnosed with MC. MC can only be confirmed with biopsy which differentiates between the two major subtypes: lymphocytic colitis (LC) and collagenous colitis (CC). Recent data suggests MC is nearly as common as classic IBD. It is typically recognized as a disease of the elderly, with an average age at diagnosis of 65 years. It is noteworthy, however, that 25% of microscopic colitis patients are younger than 45. Thirty to fifty percent of patients with MC have associated autoimmune disorders, with celiac disease being the most common. In most cases the diagnosis of the associated autoimmune disease precedes the diagnosis of MC. Microscopic colitis rarely affects children, although isolated case reports do exist. This case illustrates both the association of MC with autoimmune disorders as well as the ability of MC to occur in younger patients. With newer data suggesting a prevalence of MC higher than what was once thought, it is important to keep MC in the differential diagnosis of anyone who presents with chronic, non-bloody diarrhea, especially patients with concurrent autoimmune diseases. Furthermore, in patients with MC who fail to respond to treatment, a search for concomitant autoimmune diseases may prove helpful in reaching a diagnosis.