Severe musculoskeletal phenotype associated with an unbalanced t(6;10) translocation: clarification of the locus for this phenotype on distal 6p.

Larsen syndrome is a congenital condition consisting of multiple large joint dislocations associated with a distinctive facial appearance and frequently other abnormalities. The syndrome is probably genetically heterogeneous, with both dominant and recessive inheritance reported. Previously two cases have been reported where a Larsen-like syndrome was associated with unbalanced chromosomal translocations resulting in partial trisomy 1q and monosomy distal 6p. We now report a child with an unbalanced translocation resulting in a distal 6p deletion and partial trisomy 10q, who has Larsen-like features and has also severe developmental delay. A G-banded preparation revealed a karyotype 46,XX,der(6),t(6:10)(p25;q25.2) and the breakpoint at 6p25 was confirmed by FISH using YAC probes (between 6p25 at D6s477/F13A1 and 6p24 at 6WI13606). Our case provides further evidence for a Larsen-like locus at distal 6p and reduces the potential critical region.