[Molecular cytogenetic study of a 21p+ variant in a family with Crouzon syndrome].

A 31 year-old male with Crouzon syndrome and a 21p+ was observed. Pedigree analysis and molecular cytogenetic study on the members of the family revealed that this syndrome was an autosomal dominant disease inherited from the proband's mother, and the 21p+ was transmitted from the father. Neither large AG-band nor double NOR was observed on p+. Using a 7.3 kb fragment of 18S and 28S rRNA genes as probe, chromosomal in situ hybridization demonstrated that this p+ was very probably the result of enlargement of NOR or duplication of rRNA genes on this chromosome.