Mutations in exon 12 of JAK2 are mainly found in JAK2 V617F‐negative polycythaemia vera patients

blood counts and immune function. This patient’s transplant conditioning regimen was designed to limit exposure to agents that may cause adverse effects in children with chromosomal breakage syndromes. Use of alemtuzumab (CAMPATH-1H) and fludarabine provided the required immune suppression, while the lowest considerable dose of the alkylator melphalan was adequate to provide modest myeloablation and to ensure successful engraftment. To our knowledge, this is the first account of a reducedintensity HSCT from an unrelated donor in a patient with Seckel syndrome. One prior report described the use of a conventional transplant regimen in a Seckel syndrome patient (Esperou-Bourdeau et al, 1993). Reduced-intensity HSCT conditioning regimens have been successfully used in other bone marrow failure syndromes (Shenoy et al, 2005; Gruhn et al, 2007) and metabolic disorders (Hansen et al, 2007). Selecting an appropriate conditioning regimen for a child with Seckel syndrome is particularly challenging due to the heterogeneity of the disorder and the lack of prior reports to guide the choice. There is a high likelihood that Seckel syndrome patients will exhibit some degree of increased sensitivity to DNA damaging agents, even with normal mitomycin C or DEB chromosomal breakage studies. The preparative regimen that we selected, with emphasis on immune suppression and minimal use of DNA-damaging agents, is an attractive option for additional children with this disorder, in the absence of an available test to quantify increased sensitivity.