Musculoskeletal ImagingLeukaemia
a group of acute or chronic myeloproliferative disorders affecting children or adults (Table 1). For a general description, see
leukaemia.
Leukaemia, Table 1. Classification of leukaemias.
| Acute childhood leukaemia |
| Acute adult leukaemia |
| Chronic leukaemia |
| Hairy cell leukaemia |
| Acute megakaryoblastic leukaemia |
| Granulocytic sarcoma (chloroma) |
Acute Childhood Leukaemia
Haemorrhage or leukaemic masses may occur in the metaphyseal periosteum, subarticular bone and synovium. On radiographs, various abnormalities are seen, including
diffuse osteopenia, radiodense and radiolucent metaphyseal bands,
osteolytic lesions and periostitis. Other skeletal abnormalities include sutural diastasis in infants and children, caused by an increase in intracranial pressure.
Joint manifestations in acute childhood leukaemia may include soft tissue swelling, effusion, and juxta-articular osteoporosis. Patients often reveal hyperuricaemia, with some developing secondary gout. Epiphyseal osteonecrosis may also occur in some patients.
Acute Adult Leukaemia
Skeletal involvement is less common in adults than in children with acute leukaemia.
Radiographic features consist of nonspecific
diffuse osteopenia, discrete
osteolytic lesions and metaphyseal radiolucency. Rare findings on radiographs are large destructive lesions, periostitis, acro-osteolysis, discrete subperiosteal erosions and
focal or
diffuse osteosclerosis.
Chronic Leukaemia
The bone and joint abnormalities occurring in chronic leukaemia are less common and less severe than those of acute leukaemia. Marrow hyperplasia leading to
diffuse osteopenia and discrete
osteolytic lesions may occur. Rarely, widespread bone sclerosis is evident. Masses of leukaemic cells (
chloromas) accumulating in the soft tissues can result in subjacent bone erosion.
Soft tissue oedema, clubbing and bone destruction, a combination of findings termed leukaemic acropachy, may be seen in both adults and children. Secondary gout is also a well known complication of chronic leukaemia.
Hairy Cell Leukaemia
Hairy cell leukaemia is characterized by lymphocytes with numerous short villi resembling hairs about the cell membrane, depressed bone marrow function, splenomegaly, hepatomegaly and
lymphadenopathy. Bone involvement is uncommon, but when present the lesions tend to be solitary multiple
osteolytic lesions with predilection for the
spine and proximal portion of the femora. Bone sclerosis is rare. Infections and fractures are recognized complications in this disease.
Acute Megakaryoblastic leukaemia
This disorder, also termed
malignant myelofibrosis, is characterized by anaemia, pancytopenia and
diffuse marrow
fibrosis. In children, radiolucency in the metaphyseal regions of
tubular bones and
osteolytic lesions are seen. The degree of periostitis can be profound. In adults,
focal or
diffuse bone sclerosis is observed.
Granulocytic Sarcoma (chloroma)
In this disease, which occurs most commonly in patients with acute leukaemia of the myeloid type, soft tissue masses of immature granulocytic or leukemic cells occur. The tumour frequently has a greenish colour grossly. Sites most often affected are bone (especially the skull, spine, ribs, long tubular bones and sternum), periosteum, soft tissue, orbit, lymph nodes and skin. When bones are involved the lesions are characteristically lytic. In addition, tumours in the soft tissues may erode neighboring bones.
MR imaging has broad applications in evaluating musculoskeletal involvement in patients with leukaemia. This imaging method may help determine the extent of alterations in the bone marrow prior to the initiation of therapy, assess the response of the disease to such therapy, and allow detection of some of the skeletal complications of the disease or therapeutic regimen. Most commonly, in leukaemia the bone marrow demonstrates a decrease in signal intensity on T1-weighted spin-echo MR images (Fig. 1). T2-weighted changes are more variable and less dramatic. Quantitative chemical shift MR imaging has been used in patients with leukaemia to determine the stage of the disease. MR imaging may also be valuable in defining local complications of musculoskeletal involvement in leukaemia, such as soft tissue extension of intraosseous lesions and compromise of the spinal cord accompanying vertebral involvement.
DR/RB
DR/RB