A novel DKC1 mutation, severe combined immunodeficiency (T+B-NK-SCID) and bone marrow transplantation in an infant with Hoyeraal-Hreidarsson syndrome

X- linked Hoyeraal - Hreidarsson syndrome ( XL-HHS) is the severe infantile variant of X- linked dyskeratosis congenita ( XL- DC) and both are due to mutations in the DKC1 gene within Xq28. We report a novel missense mutation in DKC1 exon 3 ( T113 --> C, Ile38Thr) in a Sardinian infant with XL- HHS in whom the disease was characterized by 'T+B-NK- ' severe combined immunodeficiency and bone marrow failure. He underwent sibling bone marrow transplantation using a conditioning regimen fludarabine, rabbit antithymocyte globulin, low- dose melphalan) selected according to the HHS/ DC phenotype. This was associated with low toxicity, prompt engraftment with adequate immune reconstitution and full donor haemopoiesis.