Celiac disease (CD) is widely perceived as a childhood disorder. However, it has been demonstrated that 19–34% of new CD cases are diagnosed in patients over 60 years of age and lack the typical presentation. A 76-year-old female was admitted to the clinic due to a recurrent fever that had lasted over a year accompanied by progressive weakness, weight loss of about 10 kg, dehydration, and malnutrition. The patient had undergone resection of a fragment of the small intestine due to perforation and abscess 13 years previously (at which time no histopathological examinations were performed). During the current hospitalization, despite extensive laboratory, microbiological, and imaging tests, no specific diagnosis was made. Symptomatic treatment and empirical antibiotic therapy were conducted, but the patient died on the twenty-seventh day of hospitalization due to progressive respiratory failure. The autopsy revealed peripheral T-cell lymphoma in the mesentery of the small intestine, uterus, cecum, lung, and mediastinal lymph nodes. Based on the clinical picture, we believe that the lymphoma was induced by long-term, undiagnosed CD. Current knowledge allows us to see age-related differences in the manifestation of celiac disease and to be alert to the possible late-stage complications of the disease. The lack of awareness of how CD’s symptoms vary with age may lead to misdiagnosis and serious consequences of delayed diagnosis, including death.