Pediatric Langerhans Cell Histiocytosis with BRAF Mutation Affecting Sacral Vertebra: A Case Report and Disease Review.

Background:Histiocytoses are rare diseases affecting mainly children and can occur in any organ of the body. They are divided into Langerhans type and non-Langerhans type. Langerhans cell histiocytosis (LCH) mainly affects skin, bones, and lymph nodes but can also affect the hematopoietic system. Bone lesions can be critical when they involve skull base, orbit, or vertebrae and can cause permanent neurological sequelae or death. Histopathological diagnosis and molecular markers are the mainstay for accurate diagnosis. Sixty percent of LCH cases show mutation in the BRAF oncogene. They are treated with multimodality treatment which includes surgery, chemotherapy, and BRAF inhibitor therapy. Owing to the rarity of the disease and paucity of cases, the understanding and standardization of treatment is still evolving.Case Report:A 14-year-old boy presented with backache, and his imaging showed erosion of first sacral vertebral body with soft tissue component impinging and compressing the spinal canal. Histopathology and molecular diagnosis showed LCH which was positive for BRAF gene mutation. Adequate canal decompression and near-total removal of the disease load with fixation of weight-bearing axis resulted in symptomatic relief and good outcome. Systemic chemotherapy was given for the small residual disease due to fear of recurrence and impending neurological complications. He responded well to first-line therapy with vinblastine and prednisolone with complete resolution of disease on a follow-up scan.Conclusion:Accurate diagnosis with molecular markers is essential for a good outcome of LCH. Treatment of lesions at critical locations like skull base, orbit, or vertebral axis needs to be tailored to prevent permanent neurological deficits. Newer therapies in the form of BRAF inhibitors are on the way, but the efficacy and benefit need to be tested.