Chronic Watery Diarrhea With Colonic Intraepithelial Lymphocytosis Refractory To Budesonide Treatment – A Case Report

Intraepithelial lymphocytosis is a hallmark of microscopic colitis commonly presenting with debilitating chronic watery diarrhea. The exact pathophysiology remains unclear but is believed to involve an abnormal immune response to the luminal microenvironment in genetically predisposed individuals. Medications like nonsteroidal anti-inflammatory drugs, proton pump inhibitors, and antidepressants, as well as alcohol consumption and smoking have been regarded as risk factors for microscopic colitis. Lymphocytic colitis often responds well to anti-inflammatory treatment, with budesonide being a first line therapy. Relapse is common after discontinuing budesonide, often necessitating low-dose maintenance therapy. Advanced therapies including anti-TNF-alpha (e.g. infliximab) or anti-integrin (e.g. vedolizumab) agents as well as JAK inhibitors (e.g. upadacitinib) may be considered in refractory cases. However, confirmation of the diagnosis and ruling out other etiologies are necessary before intensifying treatment. Here, we present the case of a 78-year-old female patient with a twenty month history of chronic refractory diarrhea, repeatedly diagnosed as microscopic lymphocytic colitis. Following further deterioration and the development of hepatosplenomegaly with atypical liver lesions, a review of colonic biopsies and additional work-up led to the correct diagnosis.