Localisation of the gene responsible for Fechtner syndrome in a region < 600 Kb on 22q11-q13

Fechtner syndrome is an autosomal dominant disorder which has been thought to be a variant of Alport syndrome. It is characterised by nephritis, senso rineural hearing loss and eye abnormalities, as well as by macrothrombocyto penia and polymorphonuclear inclusion bodies. Recently, the Fechtner syndro me has been mapped in a 5.5 Mb region on the long arm of chromosome 22 by l inkage analysis in an extended Israeli family. We describe here the genetic refinement of the Fechtner critical interval to a region less than 600 Kb by linkage analysis performed in a large Italian pedigree. The presence of several recombination events allowed the disease gene to be localised betwe en markers D22S278 and D22S426, in a region containing only two nonrecombin ant markers, D22S1173 and D22S283. This interval, spanning < 600 Kb on geno mic DNA, has been entirely sequenced and contains six known and three putat ive genes.