The patient is a 34-year-old male with no medical history of interest, except for seborrhoeic dermatitis for the last 7 years. The patient was referred for investigation due to intermittent episodes of diarrhoea, sometimes accompanied by mucus and blood, of 6 years' duration. The following tests were performed: blood tests: eosinophilia of 600 absolute eosinophils; stool cultures: negative; stool parasites: negative; colonoscopy: serpiginous ulcers were observed in the rectum, which were biopsied, with no other alterations. Pathological examination: large intestinal mucosa with erosion, microhaemorrhages and acute inflammation with abundant eosinophils and chronic inflammation with a predominance of plasma cells.
Given the initial suspicion, given the clinical and endoscopic findings, of ulcerative colitis, treatment was started with 5-ASA, despite which the symptoms persisted. For this reason, new laboratory tests were performed (in which eosinophilia persisted), stool cultures and parasites (negative) and endoscopy. The second colonoscopy showed normal mucosa throughout, biopsies were taken from the right, transverse, left and sigmoid colon, and the pathology study showed an increase in eosinophils in the lamina propria of all the samples submitted. Given the persistence of peripheral eosinophilia and the finding of an increased number of eosinophils in the biopsies, eosinophilic gastroenteritis was suspected, and the patient was referred to the Internal Medicine and Allergy departments, where other causes of eosinophilia (asthma, allergies, endocrine pathology and hypereosinophilic syndrome) were ruled out. He also underwent gastroscopy with biopsies, which were found to be unaltered. Based on all the findings described, the patient was diagnosed with eosinophilic colitis.

