what is regressive or late onset autism

Regressive autism occurs when a child appears to develop typically but then starts to lose speech and social skills, typically between the ages of 15 and 30 months, and is subsequently diagnosed with autism

Other terms used to describe regression in children with autism are autism with regression, autistic regression, setback-type autism, and acquired autistic syndrome. There is no standard definition for regression,and the prevalence of regression varies depending on the definition used.Some children show a mixture of features, with some early delays and some later losses; and there is evidence of a continuous spectrum of behaviors, rather than a black-and-white distinction, between autism with and without regression

According to the definitions in the DSM-5 the term “regressive autism” can refer to any type of autism spectrum disorder that involves regression, including Childhood Disintegrative Disorder.