Working Diagnosis:
Langerhans cell histiocytosis

Treatment:
The patient had a curettage of the left femoral lesion with placement of a short femoral intramedullary nail. Case Photo #3

Outcome:
The patient had gradual improvement with physical therapy. Three months post-op, the patient was able to play basketball. Seven months post-op, bone scan was negative and left femoral x-ray showed resolving left femoral lesion. Thirteen months post-op, the patient had a negative bone scan and normal left femoral x-ray. The patient has not experienced systemic symptoms or symptoms consistent with femoroacetabular impingement.

Author's Comments:
Langerhans cell histiocytosis is a benign, abnormal differentiation or proliferation of phagocytic system mononuclear cells. Langerhans cell histiocytosis can manifest as a single or multisystemic disease, but most commonly occurs in bone, skin, lungs, and the pituitary. When Langerhans cell histiocytosis is limited to bone, it is considered an eosinophilic granuloma. Eosinophilic granulomas account for 60-80% of Langerhans cell histiocytosis cases, but account for less than 1% of all bone tumors. Children and adolescents account for 80% of eosinophilic granuloma cases.

Clinically, patient with eosinophilic granuloma may be asymptomatic or present with focal pain, restricted range of motion, fracture at site of lesion, or limping if lesion is located in the leg; neurologic symptoms are uncommon. Physical examination of a child may be normal and labs are usually non-specific. Radiographically, eosinophilic granuloma of extremities show punched-out lytic bone lesion without reactive sclerosis. Definitive diagnosis requires tissue biopsy.

Treatments for eosinophilic granuloma include observation and immobilization, indomethacin administration, methylprednisolone injections, radiofrequency ablation, local excision and curettage with or without bone grafting, or chemotherapy and irradiation. Typically, prognosis is good for eosinophilic granuloma.

Editor's Comments:
This case raises several interesting points regarding the diagnosis and management of eosinophilic granuloma. I do not believe that the diagnosis of femoroacetabular impingement is a key component of this case as studies have shown that 40-50% of asymptomatic individuals will have imaging findings consistent with FAI. There is no mention of specific positional hip pain that would suggest FAI. Furthermore FAI would not explain any systemic symptoms experienced by the patient. That being said, it is interesting that an intra-articular hip cortisone injection resolved all systemic symptoms within 24 hours. The proposed mechanism by which a corticosteroid injection can be used for treatment is that the Langerhans cells induce bone resorption in eosinophilic granuloma through the local production of interleukins and prostaglandins. Most injections done for eosinophilic granuloma are intralesional injections. My sense is that this injection had a more systemic effect as opposed to a local effect on the proximal femur lesion in this case.


Also, the diligence of follow-up should be commended in this case. Biopsy has a very high diagnostic accuracy so it is surprising that the initial biopsy did not confirm the diagnosis.

References:
Allen, C. E., Merad, M., and McClain, K. L. (2018). Langerhans-cell histiocytosis. New England Journal of Medicine, 379(9), 856-868.

Angelini, A., Mavrogenis, A. F., Rimonid, E., Rossi, G., and Ruggieri, P. (2017). Current concepts for the diagnosis and management of eosinophilic granuloma of bone. Journal of Orthopaedics and Traumatology, 18 (2), 83-90.

Arndt, C. A. S. (2016). Benign tumors and tumor-like processes of bone. In Kliegman, R. M., Stanton, B. F., St. Geme III, J. W., Schor, N. F. and Behrman, R. E. (Eds.) Nelson Textbook of Pediatrics (pp. 2475-2476). Elsevier: Philadelphia, PA.

Azouz, E. M., Saigal, G., Rodriguez, M. M., and Podda, A. (2005). Langerhans cell histiocytosis: pathology, imaging and treatment of skeletal involvement. Pediatric radiology, 35(2), 103-115.

Glotzbecker, M. P., Garpentieri, D. F., and Dormans, J. P. (2002). Langerhans cell histiocytosis: Clinical presentation, pathogenesis, and treatment from the LCH etiology. Univ Pa Orthop J, 15, 63-73.

Kilpatrick, S. E., Wenger, D. E., Gilchrist, G. S., Shives, T. C., Wollan, P. C., and Unni, K. K. (1995). Langerhans cell histiocytosis X) of bone and clinicopathologic analysis of 263 pediatric and adult cases. Cancer, 76(12), 2471-2484.

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