From our gene list, two genes have been previously linked to LMS sarcomagenesis—DAXX and PTPRN2. DAXX (Death Domain–Associated) forms a dimer with ATRX (Alpha-Thalassemia/Mental Retardation Syndrome X-linked) and dysfunction of this ATRX/DAXX complex is associated with alternative lengthening of telomeres (ALT), which occurs in a proportion of LMSs35–37. The gene discussed is DAXX; the disease is X-linked syndromic intellectual disability.