Table 1.

Example Reports of Regression in Syndromes Associated with Autism Spectrum Disorder

Condition	Report	Ages/Stages	Specific Skills Lost	Associations?
Kleefsta Syndrome	Kleefstra et al. (2009)	Various ages	toileting, eating, loss of interest, undefined
Phelan-McDermid Syndrome	Denayer et al. (2012) Serret et al. (2015)	Not reported 12–13 years	language, fine motor, gross motor, daily living skills, social engagement
	Reierson et al. (2017)	Range from 18 months to 18 years
Christianson Syndrome	Pescosolido et al. (2014)	Range from 15 months to 16 years	Language (words or sounds) (57%); walking (57%), eating (14%) fine motor (14%) eye contact/facial expression (14%)
15q Duplication	Conant et al. (2014)	Not reported		20/33 cases associated with epilepsy
Rett Syndrome/CDKL5	see Neul et al (2010; 2014) for reviews	Most often between 6 & 30 months	fine motor; language; gross motor
Down Syndrome	Castillo et al. (2008)	Language Loss $\overline{x}=62$ months Other skill loss $\overline{x}=46$ months	language loss; other skills (not specified)