Crohn's disease and multiple myeloma are pathological entities, the development of which, at least in part, is associated with an immune disregulation. Crohn's disease is often combined with extra-intestinal manifestations from different organs and systems (joints, skin, eyes, etc.). Hematological extra-intestinal manifestations, such as myelodysplastic syndrome, aplastic autoimmune anemia, autoimmune thrombocytopenia, B12-deficiency anemia are less common. The list of extra-intestinal manifestations of Crohn's disease is constantly expanding, including more and more descriptions of the combination of Crohn's disease with diseases of the blood system. The paper presents a rare clinical case of a combination of Crohn's disease and multiple myeloma. The female patient is 53 years old. In 1993 ulcerative colitis was diagnosed and she received Sulfasalazine 4gr per day. In 2015, with the recurrent attack, the diagnosis was transformed towards Crohn's disease basing on colonoscopy. She received steroid therapy. In 2018 the control examination revealed an increase in the level of total protein to 117gr/l. Patient underwent a sternal biopsy. Multiple myeloma was diagnosed on the basis of a myelogram.