Osteoporosis in LCH, particularly in young adults, is uncommon and may result from altered bone remodeling because of Langerhans cell infiltration, which stimulates osteoclast activity via inflammatory cytokines such as IL-1, TNF-α, and RANKL, leading to bone resorption [11]. The gene discussed is TNFSF11; the disease is Langerhans cell histiocytosis.