Terminal deletions of chromosome 15q are relatively rare chromosomal anomalies that are usually associated with variable degrees of pre-and post-natal growth failure and are sometimes accompanied by mental retardation and/or congenital anomalies such as congenital heart defect (CHD) [1] . In this regard, haploinsufficiency of the gene for insulin-like growth factor 1 receptor (IGF1R) at 15q26.3 is known to be relevant to the growth failure and mental retardation [2] , and hemizygosity of the

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... e for nuclear receptor subfamily group F member 2 (NR2F2) at 15q26.2 has been postulated as an underlying factor for CHD [3] [4] [5] [6] . The chromosome end is associated with 3-20 kb of tandemly repeated telomere sequences (TTAGGG) n that are extended and maintained in human germline by telomerase using an integral telomere-complementary RNA template [7] [8] [9] . The telomere sequences are essential for chromosome stability and DNA replica-abstract. We report a de novo heterozygous 5,013,940 bp terminal deletion of chromosome 15q26 in a 13 9/12 -year-old Japanese girl with short stature (-3.9 SD), mild mental retardation, and ventricular septal defect (VSD). This terminal deletion involved IGF1R but not NR2F2, and was associated with an addition of telomere repeat sequences (TTAGGG) at the end of the truncated chromosome. The results provide further support for the notion that terminal deletions are healed by de novo addition of telomere sequences essential for chromosome stability and DNA replication. Furthermore, while growth failure and mental retardation are primarily explained by loss of IGF1R, the occurrence of VSD might suggest the existence of a cardiac anomaly gene, other than the candidate cardiac anomaly gene NR2F2, in the deleted region.