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 more commonly associated with autism spectrum disorder and may be present in Rett syndrome, but it is not specific enough to distinguish between the two. Choice B reason: Lack of imaginative play is also more typical in autism spectrum disorder and may not definitively point toward Rett syndrome. Choice C reason: Deceleration of head growth (microcephaly) around 6 months is a hallmark feature of Rett syndrome, distinguishing it from autism spectrum disorder, which usually does not present with postnatal deceleration in head circumference. Choice D reason: Lack of eye contact can be observed in autism spectrum disorder and is not unique to Rett syndrome, making it less useful for differential diagnosis.