Working Diagnosis:
Pathologic Salter-Harris Type II fracture of the right postero-lateral proximal tibia due to underlying precursor B-cell acute lymphoblastic leukemia (ALL)

Treatment:
His induction lasted 35 days with Cytarabine intrathecally (IT) on day 1, Vincristine IV on days 1, 8, 15, and 22, Dexamethasone IV or orally twice daily on days 1-28, Pegaspargase IV on day 4, and Methotrexate IT on days 8 and 29. Consolidation for 19 weeks began on day 36 while maintenance consisting of 16 week cycles for 2.5 years started after that.

His fracture treatment consisted of a long leg cast with the right knee in slight flexion and non-weight bearing for 6-8 weeks. Close follow up was required to ensure healing and to ensure no signs of vascular compromise.

Outcome:
His proximal tibial pathologic fracture was healed two and a half months after his initial visit. He had some deconditioning but still had full range of motion.

One day after diagnosis, chemotherapy was initiated following the COG AALL0932 protocol. This patient had a favorable prognosis due to his WBC count, age, no CSF involvement, and cytogenetics consisting of trisomy 4 and 10.

His induction phase was completed in 29 days, leading to remission with negative end of induction morphology.
There was no evidence of previous immunophenotyped B lymphoblastic leukemia or lymphoma on bone marrow aspirate. Three months after diagnosis, he was cleared for activity without restrictions. He was advised to return if new pain develops. Maintenance chemotherapy will be continued until 2.5 years have passed from diagnosis date.

Author's Comments:
This patient's lab values were consistent with Hemoglobin E trait and anemia of chronic disease. Pathological fractures in children diagnosed with acute lymphoblastic leukemia on initial presentation have been reported 5.7-12% of the time. Osteopenia can be seen post-treatment up to 20 years. ALL is the most diagnosed cancer in children under the age of 15 (Approximately 41 cases per 1 million children age 0-14 years in the United States). Typical presentation of ALL includes general fatigue symptoms, fever, easy bruising, and bone pain. Biopsy is needed for diagnosis. Treatment involves years of chemotherapy based on individual risk classification. Current regimens of treatment achieve over a 90% survival rate at 5 years.
But, allowing children with ALL to return to physical activity as tolerated after fractures have healed is important due to the positive impact on bone, muscle, cardiovascular, and mental health.

Editor's Comments:
Salter-Harris tibial plateau fractures are relatively rare. The physis in pediatric patients are highly vascular, predisposing them to infection and metastatic cancer, among others. Hence, pain out of proportion to the injury, pediatric limping, joint effusion, unexplained fever, unexplained weight loss, and especially pathologic fractures should be met with high indices of suspicion for other underlying causes such as leukemia, even with or without minor trauma.

References:
1. Luca DC. Update on Lymphoblastic Leukemia and Lymphoma. Clin Lab Med. 2021;41(3):405-416.

2. Xu H, Yu H, Jin R, Wu X, Chen H. Genetic and Epigenetic Targeting Therapy for Pediatric Acute Lymphoblastic Leukemia. Cells. 2021;10(12):3349.

3. Pecheux L, Forget P, Geurten C, Rausin L, Nicolescu R, Hoyoux C. Bone disorders and complications of pediatric acute lymphoblastic leukemia: monocentric study and review of the literature. Rev Med Liege. 2018;73(11):575-582.

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