P189 – 2279: Is the regression period in Rett syndrome well defined and easy to recognize?

Objective In order to increase knowledge of regression as a clue to diagnose Rett syndrome (RTT), we want to investigate if the regression period (RP) is well defined and easy to recognize. Methods Medical records (including questionnaires and interviews) were reviewed concerning the RP in children with clinical Rett syndrome and a MECP2 mutation referred to the nation-wide Centre for Rett syndrome in Denmark in the years 2012–2014. Results Ten girls with RTT (8 typical/2 atypical) and a MECP2 mutation aged 1.7–5.3 years (mean 3.3 years; median 2.8 years) were referred to the centre and evaluated within 13–152 days (mean 58.3 days; median 41.5 days). Seven of the girls were post regression at this first evaluation. In the other 3 cases it was difficult to conclude but time showed that 2 girls were still in regression at the first visit. The girls were in RP in the range of about 4–35 months (mean 14.8 mo; median 12 mo). Before the RTT diagnosis 5 of the girls were referred to psychiatric evaluation at a time that turned out to be in the RP. One of these girls and 3 others had a muscular biopsy before (2), under (1) or after (1) an unrecognized RP. One girl had severe symptoms of epilepsy and adverse reactions to medication in RP. In 6 cases the RP along with other symptoms as handstereotypies led to suspicion of RTT. Five of the girls were diagnosed in the RP and the other 5 after the RP. Conclusion In most of our cases, RP was not well defined or easily recognized. It might be overlooked because of its long and slow progression as well as co-morbidities like hypotonia or epilepsy. We conclude that more information regarding regression in RTT is needed to facilitate early diagnosis, counselling and treatment.