Three main types of developmental delay that pediatricians should know and understand are Aspberger syndrome, autism, and global developmental delay. Knowing the distinctions between the types of developmental delay and MR can lead to earlier diagnosis and referral for appropriate services and may have a positive effect on the long-term outcomes for affected children and their families.

According to the Diagnostic and Statistical Manual of Mental Disorders, 4th ed.; (DSM-IV) individuals with MR have an intelligence quotient (IQ) <70 and concurrent impairments in adaptive functioning in at least two of the following areas: communication, self-care, home living, social or interpersonal skills, use of community resources, self-direction, functional academic skills, work, leisure, health, and safety. MR must be diagnosed before age 18. The degree of MR is delineated by the IQ score, with an IQ of 55 to 69 signaling mild MR, an IQ of 40 to 54 signaling moderate MR, an IQ of 25 to 39 signaling severe MR, and an IQ of <24 signaling profound MR. The IQ level above which a child with MR is expected to benefit from a formal educational program is 50.

Although IQ testing is possible in the preschool years, the diagnosis of MR is usually not applied until the child reaches school age, when IQ testing is considered more reliable and reflective of the child’s long-term abilities. Prior to that time, a diagnosis of “global developmental delay” is used and is sufficient to access appropriate support services within schools and public agencies.

Autism and Asperger syndrome are the two most common conditions classified as pervasive developmental disorders (PDDs). Often described as “autism spectrum disorders,” these PDDs are marked by three central characteristics: impairments in social reciprocity, impairments in communication, and abnormalities of behavior.

Children with autism and Asperger syndrome both have impaired social learning. They often exhibit disabilities in initiating, responding to, and maintaining social interactions. They have particular difficulty with nonverbal communication, such as eye contact, gestures, and voice inflection. They have trouble integrating verbal and nonverbal components of communication. Most of these children have difficulty engaging in the “give–and-take” of social interactions.

Autism and Asperger syndrome are both characterized by communication impairments, and the degree of impairment helps define the differences between these syndromes. In children with autism, language is severely delayed and unusual or deviant, in both expressive and receptive areas. Cooing and babbling may develop in the first 6 months of life but then be lost, and speech develops late or not at all. In contrast, children with Asperger syndrome do not show delays in speech. When expressive language develops in children with PDD, it has impaired pragmatics. Early language often consists of echolalia and use of certain “stock phrases” or repetition of conversation from television. Other characteristics include confusion of personal pronouns, verbal perseveration (repeating something over and over or dwelling on a specific subject), and abnormalities of prosody (modulation of volume, pitch, rate of speaking). Although children with Asperger syndrome may have strong vocabularies, their language deficits include lack of “turn-taking” in conversations, preoccupation with their own areas of special interest, tangential or off-topic responses, and problems with abstract language.