A GENE FOR ACHONDROPLASIA-HYPOCHONDROPLASIA MAPS TO CHROMOSOME 4P

Achondroplasia (ACH) is a frequent condition of unknown origin charact erized by short-limbed dwarfism and macrocephaly. Milder forms, termed hypochondroplasias (HCH) result in short stature with radiological fe atures similar to those observed in ACH. We report on the mapping of a gene causing ACH/HCH to human chromosome 4p16.3, by linkage to the id uronidase A (IDUA) locus, in 15 informative families (Z max = 3.01 at theta = 0 for ACH; Z max = 4.71 at theta = 0 for ACH/HCH). Multipoint linkage analysis provides evidence for mapping the disease locus telom eric to D4S412 (location score in log 10 = 4.60). Moreover, this study supports the view that ACH and HCH are genetically homogeneous in our series.