I. Also known as "Pervasive Developmental Disorder"--A set of developmental abnormalities affective social, verbal, and nonverbal function, and involving rigid repetitive behaviors.  There are many possible underlying causes.  Usually grouped into the following categories:

  1. Autistic Disorder--The most "classic" of the PDDs; often, though not exclusively, associated with inability to live independently as an adult
  2. Asperger Disorder--Difficulties are centered around social interactions; tend to have narrow interests; IQ usually > 70
  3. Disintegrative Disorder--Characterized by normal development until onset at 2-10yo followed by severe regression
  4. Rett Syndrome--X-linked; seen almost exclusively in girls; characterized by severe mental retardation; also usually by severe motor deficits and epilepsy
  5. PDD not otherwise specified--Used to describe those who don't fit into one of the other categories

II. Epidemiology

  1. Prevalence in U.S. children about 0.9% as of 2010

III. Symptomatology

  1. 70-95% of children have identifiable symtpoms by 3yo
  2. Verbal function
    1. Failure to develop, or regression of, verbal expression or communicative gestures (with hands or head, e.g. head shaking to indicate "no")
    2. Mutism unpredictably interrupted by clearly-articulated words
    3. Lack of speech comprehension
    4. Inability to speak conversationally or tell a story, i.e. speaks but without apparent intent to communicate
      1. Echolalia (frequent, persistent, verbatim repetition of words or sounds)
      2. "Formulaic" speech (repeats learned expressions, especially technical or pedantic expressions, rather than generating his/her own expressions appropriate to the situation)
    5. Pronoun inversion (e.g. interchanging "you" and "me")
    6. Perseveration on a particular topic of speech
    7. Persistently high-pitched, sing-song, or uninflected ("robotic") speech
  3. Social function
    1. Unprovoked aggression
    2. Severe tantrums
    3. Lack of attention to or acknowledgement of others
  4. Nonverbal function
    1. Monotonous, unimaginative play
    2. Adherence to rigid routines with temper tantrums if these are interrupted
    3. Stereotyped motor behavior (e.g. rocking, hand flapping)
    4. "Clumsiness"
    5. Intolerance to loud sounds

IV. Probable/known causes--Generally < 20% of cases have an idenfitiable cause

  1. Infections (rubella, cytomegalovirus, herpes simplex)
  2. Ischemic brain damage
  3. Thalidomide exposure in utero
  4. Tuberous sclerosis
  5. Untreated phenylketonuria
  6. Fragile X syndrome
  7. Lead poisoning

V. Screening

  1. As of 2006, the AMerican Academy of Pediatrics recommends developmental sureillance at every preventive care visit, standardized general screening tests at 9mo, 18mos, and 30mo, and autism-specific screening at 18mo and 24mos (see Pediatrics 120:1183-1215, 2007)
  2. Screening instruments:
    1. Modified Checklist for Autism in Toddlers ("M-CHAT")-May have low positive predictive value (AFP 8/15/2011)
    2. Infant-Toddler Checklist (screens for autism and language delay from 9-24mo, sensitivity for autism > 90% and positive predictive value for language disorders > 70%).

(Sources include JAMA 285:1749, 2001--AFP)