Working Diagnosis:
Langerhans Cell Histiocytosis

Treatment:
Observation with periodic MRI for surveillance

Outcome:
The patient's sports participation was deferred pending oncology assessment. A gradual return to activity was initiated. He completed 8 weeks of physical therapy successfully. At that time, he was cleared to continue basketball without restrictions.

Author's Comments:
This case describes Langerhans cell histiocytosis presenting as elbow pain in a child, initially mimicking a healing fracture. It typically presents as bone pain with swelling or a pathologic fracture. Langerhans cell histiocytosis is a rare myeloid neoplasm with an incidence of 5-9 per 1,000,000 children under 15, caused by clonal proliferation of Langerhans-type dendritic cells. It may involve a single bone or multiple organs. Diagnosis combines imaging and biopsy showing CD1a/S100-positive histiocytes; PET scans assess multi-system disease. Single-system Langerhans cell histiocytosis is treated locally, while multi-system disease requires vinblastine and prednisone for 12 months. Relapse occurs in 30-50% of cases.

Editor's Comments:
Supracondylar fractures are most common in younger children between ages 5-7. This case, which presents as a pathologic fracture secondary to Langerhans cell histiocytosis, represents a particularly uncommon clinical presentation. X-rays are typically sufficient for diagnosis, however in uncommon cases further investigation with MRI is warranted. Such instances may include when X-rays show a posterior fat pad sign or effusion alone, which may indicate presence of an occult fracture. Gartland Type I fractures can be treated non-operatively with a long arm cast for 3 weeks. All other supracondylar fractures should be referred to orthopedics for consideration of closed reduction and percutaneous pinning.

References:
1. Haroche J, Cohen-Aubart F, Rollins BJ, et al. Histiocytoses: emerging neoplasia behind inflammation. Lancet Oncol. 2017;18(2):e113�"e125.
2. Emile JF, Cohen-Aubart F, Collin M, et al. Histiocytosis. Lancet. 2021;398(10299):157�"170.
3. Rodriguez-Galindo C, Allen CE. Langerhans cell histiocytosis. Blood. 2020;135(16):1319�"1331.
4. Allen CE, Merad M, McClain KL. Langerhans-cell histiocytosis. N Engl J Med. 2018;379(9):856�"868.
5. U.S. National Library of Medicine. Langerhans cell histiocytosis. MedlinePlus Genetics. Accessed October 28, 2025.
6. Howard A, Mulpuri K, Abel M, et al. The Treatment of Pediatric Supracondylar Humerus Fractures Journal of the American Academy of Orthopaedic Surgeons. 2012;20(5):320-327. doi:10.5435/JAAOS-20-05-320
7. Davis ML, Della Rocca GJ, Brenner M, et al. Best Practices in the Management of Orthopedic Trauma. American College of Surgeons; 2015

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