Findings: Two-view films of both extremities were obtained. There are epiphyseal bony changes seen. Both sclerotic and lucent areas are identified particularly about the knee. This is more obvious in the distal left femoral metaphysis than elsewhere.

In the proximal left tibial metaphysis there is subchondral bone collapse suggesting fracture. There is associated soft tissue edema when compared to the right side.

In addition, there is a very subtle lucency in the anterior distal left tibial metaphysis which may represent fracture. No soft tissue edema is seen. Mild left metatarus adductus consistent with patient's history of left clubfoot. There is discrepancy in amount of muscular mass in the left calf compared to the right presumed related to clubfoot.

Diagnosis: Acute lymphocytic leukemia (ALL.)

Discussion: ALL is the most common malignancy of childhood. It is abnormal lymphoid cells that initially proliferate in the bone marrow before spreading to the peripheral blood, spleen, lymph nodes and eventually any tissue. There is usually a defect in the white blood cell maturation beyond the lymphoblastic stage. The etiology is not known, however genetic and environmental factors are said to be involved. Incidence is 13 per 100,000/year (includes all leukemias) and is usually higher in boys. Children present with nonspecific symptoms which may mimic infection or inflammation, fever, elevated ESR, hepatosplenomegaly, and occasionally lymphadenopathy. The peak onset age is 4 years old.

Radiographic skeletal changes are seen in 50-70% of children with leukemia and include:

1. Diffuse Osteopenia: Osteopenia with medullary widening and cortical thinning encountered in tubular bones along with vertebral compression.
2. Radiolucent & Radiodense Metaphyseal Bands: Seen in children with leukemia and other chronic diseases. Presence of symmetric metaphyseal band-like radiolucent areas. Most often due to a nutritional deficit that interferes with osteogenesis. Commonly seen in the distal femur, proximal tibia, proximal humerus and distal radius. Of note, if seen in a child > 2 years of age consider leukemia.
3. Osteolytic Lesions: Radiolucency seen with bone destruction in tubular and flat bones. This can extend into the diaphysis.
4. Periostitic: In lytic lesions periosteal bone formation can be seen. Usually collections of leukemic cells and hemorrhage in the subperiosteum.
5. Articular Abnormalities: Soft tissue swelling, effusion and juxtaarticular osteoporosis can be seen usually due to the sequestration of leukemic cells and hemorrhage in the joint space.
6. DDX: Child abuse, infection.

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