Background The following manifestations of graft-versus-host disease damaging the musculoskeletal system were described: fasciitis, stiffness, myositis, arthralgia and arthritis. But we did not find any descriptions of the hemarthrosis.

Objectives We present a case report.

Results A 43-year-old man presents in June 2015 with pain in his left knee and left hip, swelling of left knee, subfebrile temperature.

Chronic myelogenous leukemia (CML) was diagnosed in July 2014, Imatinib therapy started. In 12.19.2014 an allogeneic bone marrow transplantation was made, and then the patient receives calcineurin blockers (cyclosporine A), and prednisone. In the early postoperative period cytopenia (the lowest level of white blood cell was 0,9 × 103/μL, platelets was 27 × 103/μL,) and diarrhea were recorded. In February 2015 appeared the pain in the joints, first they were weakly expressed, but to May 2015 pain had reached 70–80 mm by VAS.

Hematologist assumed the reactive arthritis, amoxicillin/clavulanate (14 days) and metamizol were given. The treatment was ineffective, and the patient referred to rheumatologist.

On examination, his temperature was 37.2 °C. Skin and mucosa were pale with no rash. Mucosa is wet. Physical examination confirmed swelling in the knee, as well as tenderness in the areas, left knee flexion was limited to 110°. Also there was a significant movement limitation of the left hip joint. His lungs are clear to auscultation. His cardiac is unremarkable. He has palpable hepatomegaly but no splenomegaly. There is no clinical evidence of ascites

Initially we excluded septic arthritis especially tuberculosis. The initial laboratory analysis reveals white blood cell count of 9.06 × 103/μL, platelets of 30 × 103/μL, hemoglobin of 7,6 g/dL Procalcitonin serum <0.5 ng/ml (normal level). Blood cultures twice - negative result. Results of the left hip MRI were alarming. There were established the thickening of the synovial membrane, increased number of non-uniform fluid in the joint and cartilage plates damages which should have been differentiated between the previous osteoarthritis and secondary lesions on the background of a septic (tuberculosis) process. MRI results of the left knee: synovium cover thickening with areas of hemorrhagic impregnation. Synovitis.

Enzyme immunoassay serum to M.tuberculosis, also as QuantiFERON test - negative.

The synovial fluid tests show: white blood cell count of 4625 cells/ml, polymorphonuclear leukocyte 74%, erythrocytes of 50–70 in sight, crystals and culture isolation were not found.

Conclusions Thus, we excluded septic genesis of arthritis. Considering hemorrhagic content (date of MRI and synovial fluid), and in our opinion the platelet count has not reached critical level for the development of hemarthrosis, we have assumed the existence of graft-versus-host desease. During the further observation for 3 months with continued cyclosporine A and prednisolone therapy, CML did not relapse, and joint complaints completely regressed.

This is one of the first cases which describe hemarthrosis as graft versus host desease.

Disclosure of Interest None declared