A related disorder with the cancer predisposition of XP combined with the neurodevelopmental complications of CS (XPCS), although rare, has also been described [18].
Many XPD mutations are associated with an exclusive disease phenotype (e.g., XPDR722W with TTD and XPDR683W with XP) and are thus viewed as causative of the corresponding syndromes. Alleles not associated exclusively with one disorder are considered “