Celiac disease is a genetic disorder, presenting with malabsorption-related problems because of mucosal damage after ingestion of gluten. The only known effective treatment is a gluten-free diet. Early diagnosis and treatment are essential in preventing complications due to malabsorption. Here we report the case of an elderly patient with a fifteen-year history of diarrhea, diagnosed with celiac disease, who had developed several complications due to malabsorption such as anemia, electrolyte imbalance and osteoporosis. We believe that late diagnosis of celiac disease had played a great role in the development of complications. Moreover, celiac disease poses an increased risk for all types of malignancies. Our patient also had concurrent plasma cell dyscrasia, but did not fulfil the criteria for diagnosis of multiple myeloma.