In a 6-year-old girl referred because of mild motor delay and hyperextensible joints, chromosome analysis disclosed a derivative chromosome consisting of end-to-end fusion of chromosomes 2 and 14. Two cell lines existed in which this telomere association was present, one with a 45,XX,tas(2;14)(q37;p11) karyotype and one with a 45,XX,tas(2;14) (q37;q32) karyotype. The cell line with the telomeric fusion of 2q and 14p was present in 90% of the cells; a telomeric fusion of 2q and 14q was seen in the remaining 10% of the cells. In both association complexes, only the centromere of chromosome 14 was active. Fluorescence in situ hybridization with telomere and subtelomere probes disclosed no deletion of chromosomal material. Microsatellite analysis showed that the patient had a normal biparental contribution of chromosomes 14.Close