Overlap of dyskeratosis congenita with the Hoyeraal-Hreidarsson syndrome

X-linked dyskeratosis congenita (DKC) is characterized by mucosal leulropla kia and ulcerations, skin abnormalities, nail dystrophy, and pancytopenia. Hoyeraal-Hreidarsson syndrome (HHS) includes intrauterine growth retardatio n, microcephaly, mental retardation, cerebellar malformation, and pancytope nia. A patient with striking features of both HHS and DKC has a de novo mut ation in the DKC1 gene, known to be responsible Eor DKC. HHS may be a sever e form of DKC, in which affected individuals die before characteristic muco cutaneous features develop.