GENETIC-ANALYSIS IN A FAMILY WITH X-LINKE D INCOMPLETE TYPE OF CONGENITAL STATIONARY NIGHTBLINDNESS (CSNBI)

Purpose We describe particular clinical features in a three-generation family with X-linked CSNBi and present the genetic analysis. Method T he diagnosis of CSNBi was established on clinical and electrophysiolog ical criteria. Polymorphic DNA markers of the Xp region were analyzed by fluorescent polymerase chain reaction. Results Clinical findings ev idenced an atypical association of both myopia and hyperopia in the sa me br-other-hood. The most interesting feature in this family was the observation of major worsening of the clinical shape between the first and the third generation of affected individuals. DNA analysis did no t show significant linkage between the disease and markers of the Xp11 -p21 region. Southern analysis did not show expansion of trinucleotid repeat CAG/CTG and CCG/CGG over the three generation. Conclusion Haplo typic analysis together with clinical observations allow to exclude th e existence of a myopia gene closely linked to the CSNB2 locus. The cl inical anticipation observed in this family does not seem To be linked with trinucleotid repeat expansion CAG/CTG or CCG/CGG.