A Rare Case of Collagenous Colitis in a Patient With Common Variable Immunodeficiency

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Common variable immunodeficiency (CVID) is the most prevalent form of severe antibody deficiency in adults, and can present with chronic diarrhea. Collagenous colitis (CC), a subtype of microscopic colitis, is a rare condition that presents with persistent secretory diarrhea. Here, we describe a case of a man with both CC and CVID. A 23 year-old man was referred to GI after 2 visits to the ED for several months of intractable intermittent watery diarrhea and signs of malabsorption. Prior to presenting to our institution, the patient was admitted 3 times for diarrhea and abdominal pain, treated with metronidazole for presumed infectious diarrhea, and with rifaximin for small intestinal bacterial overgrowth (SIBO). Treatments produced temporary relief. On presentation to our institution, he reported 20 watery, non-bloody bowel movements daily, diffuse abdominal pain, and an 8-pound weight loss over 3 weeks. Initial labs were notable for an elevated CRP of 90mg/L (normal < 5 mg/L) and negative celiac serologies. Stool studies were negative for infection, and fecal calprotectin was minimally elevated. Stool electrolytes showed an osmotic gap < 50 mOsm/kg, consistent with a secretory diarrhea. Further testing revealed significantly decreased levels of IgA, IgG, and IgM, leading to a diagnosis of CVID. Further questioning at this time revealed a history of childhood sinusitis and Salmonella gastroenteritis. EGD revealed no small bowel endoscopic or histologic abnormality. A diagnosis of CC was made on colonic mucosal biopsy. The patient was treated with budesonide with complete resolution of symptoms. There are 7 reported cases of CVID associated with CC. CC has an estimated incidence of 4/100,000 person years, with a clear female predominance, and mean age of diagnosis of 65. Classic findings on histopathology include a thickened subepithelial collagenous band. With CVID, a condition of autoimmune dysregulation with an incidence of 1/100,000, concomitant autoimmune diseases are present in roughly 25% of patients, and can often be the presenting disorder. Persistent diarrhea is itself a fairly common presentation of CVID, but is more often due to infection, SIBO, celiac sprue, or villous atrophy.Chronic diarrhea is a common presenting symptom of CVID, but is rarely attributed to CC. As seen with our patient, a heightened suspicion for atypical presentations of immune-mediated causes of intractable diarrhea is warranted in the context of a CVID diagnosis.