Epidemiology
A clonal histiocytic disease that frequently affects bone in children, although it can also be seen in adults. It is not a sarcoma or a classic intermediate bone tumor: it can range from a single bone lesion to multisystem disease. A single lesion can be treated in a limited way, but multiple lesions or systemic involvement require pediatric or oncologic evaluation.
Basic features
It can present as localized pain, a lytic (bone-thinning) lesion, or multifocal involvement, with or without other organs affected (skin, pituitary gland, lung, liver, spleen, or bone marrow). For this reason, the evaluation aims to determine whether the involvement is single or multisystem.
Usual treatment
Management ranges from observation or curettage to systemic therapy, depending on the number of lesions, the location, and the organs affected; multisystem disease is managed by the appropriate hemato-oncology team, and in resistant or high-risk cases targeted therapies against the MAPK pathway are used (for example, BRAF inhibitors when the BRAF V600E mutation is present, which is found in a substantial proportion of cases).
Outcomes and prognosis
Single bone involvement usually has a favorable prognosis. Multisystem disease, especially with risk organs involved, has a worse prognosis and requires close follow-up.