A disease associated with immunoglobulin IgG4 is a rare unit with very variable symptoms. We describe the course and treatment of the disease in a patient who presented with multiple lymphadenopathy and infiltrates in the area of the retroperitoneum and pelvis and signs of chronic sclerosing pancreatitis. The disease was clinically manifested by a significant loss of weight, but also by a loss of perception of taste and smell. The diagnosis was made based on a high amount of IgG4 expressing plasma cells in the sampled tissue and an increased concentration of immunoglobulins of type IgG and mainly subclass IG4. Rituximab in 475 mg/m2 dose was used in the treatment, the initial four doses of rituximab were administered at 14-day intervals, always with a one-off administration of a 40 mg dose of dexamethasone. According to FDG-PET/CT, only partial remission of the disease was reached after 4 applications of rituximab and dexamethasone. The patient recovered its sense of smell and taste. In another 4 cycles ritu-ximab was administered on day 1 of a 28-day cycle. On days 1 and 15 of the cycle dexamethasone at 40 mg and cyclophosphamide at 600 mg were administered by intravenous infusion. After the completion of 8 cycles of treatment based on rituximab and dexamethasone and with cyclophosphamide added in the second half of the treatment, the control FDG-PET/CT examination proved the complete remission. Before the treatment commencement the concentration of the subclass of immunoglobulin IgG4 was equal to 51.0 g/l, after the completion of the aforementioned treatment it dropped to 3.5 g/l. The patient tolerated the treatment without any adverse effects. Ritu-ximab, dexamethasone and cyclophosphamide induced the complete remission of this disease.Key words: IgG4-associated/releated disease - rituximab.