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The first genetically described population based study in Rett syndrome—a childhood developmental disorder—has provided a more complete clinical picture to enable correct diagnosis and prognostication. It provides invaluable information for future studies on genotype-phenotype interactions too.
The study used phenotypic data from the Australian Rett Syndrome Database population registry from 1993 onwards, supplemented with information from a follow up questionnaire to each family in the first half of 2000. Blood samples were taken from the children to test for MECP2 gene mutation. The phenotypic data were used to describe variation in the syndrome according to different severity scales for Rett syndrome—Kerr, Percy, and Pineda scales—and to calculate WeeFIM (Functional Independence Measure for Children) score.
In all, 161 verified cases were eligible for the study. The families of 152 affected children responded to the questionnaire. The researchers judged 55% to be classic cases, 26% early onset atypical cases, and 19% mild atypical cases. The proportion of classic cases in the oldest group was almost twice that of the youngest (73% v 42%). Results of genetic screening were available for 134 (88%) of the sample and showed MECP2 mutation in 72%: 73% in classic, 62% early onset atypical, and 80% mild atypical cases. The four scales provided detailed information on severity and how age changed some criteria.
Rett syndrome results in impaired development usually starting about age 6 months. Population based research, say the researchers, “is still, after nearly 20 years, not yet informing treatment or intervention for Rett patients.”