RETT-SYNDROME - GEOGRAPHIC-VARIATION IN PREVALENCE IN NORWAY

The prevalence of Rett syndrome is reported for three Norwegian counti es (Rogaland, Ostfold and Nordland). The total number of females betwe en 3 and 19 years of age in these counties was 96 920, and among these 21 females with Rett syndrome were identified, yielding a prevalence rate for Rett syndrome of 2.17 per 10 000 girls. One reason for this c omparatively high prevalence rate might be that the full spectrum of R ett syndrome variants was included. The quality of the health care sys tem and the awareness of Rett syndrome and its variants among Norwegia n physicians also make it unlikely that many cases were missed. Howeve r, the high total prevalence was caused by a statistically significant larger number of girls with Rett syndrome in Rogaland than in the oth er two counties. Sixteen of the girls were identified in Rogaland coun ty, which gives a prevalence rate for this county of 3.77 per 10 000 g irls. The prevalence rates in the two other counties were 1.05 and 0.7 7 per 10 000 girls. The geographical distribution of girls with Rett s yndrome in Rogaland is probably due to genetic clustering. Geographica l mobility in Norway is limited and many families have lived in the sa me geographical area for generations. An explanation based on genetic clustering is also supported by the fact that several of the girls wit h Rett syndrome in Rogaland county are known to be related. (C) 1997 E lsevier Science B.V.