The expressive and receptive language development of a 5-year-old girl is severely impaired. The child also displays severe psychomotor retardation, poorly coordinated gait and trunk movements, and stereotypic hand movements. What other associated features would lead the PMHNP to suspect a diagnosis of Rett syndrome rather than autism spectrum disorder in this patient?

Choice A reason: Lack of social engagement is common in autism spectrum disorder and is not specific for Rett syndrome. Choice B reason: Lack of imaginative play is also a feature of autism spectrum disorder, making it nonspecific for Rett syndrome. Choice C reason: This is the correct answer. A hallmark of Rett syndrome is deceleration of head growth beginning around 6 months of age. This feature, in combination with severe psychomotor impairment and stereotypic hand movements, helps differentiate Rett syndrome from autism. Choice D reason: Lack of eye contact is common in autism spectrum disorder and is not a distinguishing feature of Rett syndrome.