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, sensorineural hearing loss and eye abnormalities, as well as by macrothrombocytopenia and polymorphonuclear inclusion bodies. Recently, the Fechtner syndrome has been mapped in a 5.5 Mb region on the long arm of chromosome 22 by linkage 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 between markers D22S278 and D22S426, in a region containing only two nonrecombinant markers, D22S1173 and D22S283. This interval, spanning < 600 Kb on genomic DNA, has been entirely sequenced and contains six known and three putative genes.