In terms of LCH onset, a higher proportion of patients under 3 years of age had BRAF mutations in exon 15 and MAP2K1 mutations in exon 2 compared to those with BRAF mutations in exon 12 and MAP2K1 mutations in exon 3 (p = 0.037; p = 0.0015). The gene discussed is BRAF; the disease is Langerhans cell histiocytosis.