A 55-year-old woman had suffered from diarrhea and a weight loss of 15 kg over the previous six months. Neither the search for a causative pathogen nor coloscopy had provided a diagnosis. She was known to have type 1 diabetes mellitus, previous Hashimoto's thyroiditis, rheumatoid arthritis treated with leflunomide and drug- treated arterial hypertension. She was in a reduced general condition.
: The results of extensive initial diagnostic tests were unremarkable. Biopsies obtained at colonoscopy revealed marked lymphocytic colitis (LC).
When leflunomide was discontinued and replaced by salazosulfapyridine (sulfasalazine) and the steroid budesonide, the diarrhea ceased within a few days and the LC was no longer evident histologically after three months.
Leflunomide can in rare cases cause a LC. that can quickly regress once the drug has been stopped. If the findings on colonoscopy in a case of otherwise unexplained diarrhea are grossly normal, a biopsy should be taken to rule out microscopic colitis.