This disorder includes a spectrum of behavioral problems commonly associated with autism. The Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) includes autistic disorder, Rett syndrome, childhood disintegrative disorder, Asperger disorder, and PDD not otherwise specified under the spectrum of PDD. The DSM-IV groups these disorders together because they share behavioral problems in the area of social interaction and communication. Other symptoms include stereotyped behaviors, restrictive interests or activities, and cognitive deficits.
Autistic disorder in its most severe presentation may describe a child aged 3 years who presents with no expressive language, who seeks comfort from parents in atypical ways, who engages in repetitive hand flapping, and who makes no eye contact. In the mildest presentation, PDD not otherwise specified may describe a child aged 9 years with poor peer interactions, normal verbal abilities, and mild nonverbal disabilities. The mild nonverbal disabilities make it difficult for the child to follow subtle social cues that most children easily interpret as anxiety, anger, or sadness. The child's preoccupation with a restricted interest and attention to detail often tires the patience of peers with similar interests who are developing normally.
Symptoms of PDDs that may begin during the first year of life include lack of joint attention. A normally developing 1-year-old infant would make eye contact with a parent, point at an object for the parent to see, and smile responsively if the parent identifies the object. A child at risk for PDD often lacks these behaviors. Some such children may escape clinical attention until adolescence. Adolescents with normal development begin to use abstract thinking, realize that people have differing opinions, and learn to accept them. Adolescents with PDD often present with rigid thinking, are unable to accept other's opinions, and explode behaviorally when they cannot convince others to adhere only to their opinion.
Identified organic disorders that occur with PDD include epilepsy (the most common medical condition associated with PDD), cerebral palsy, fragile X syndrome, fragile X premutation involvement, tuberous sclerosis, phenylketonuria, neurofibromatosis, Down syndrome, and congenital rubella. Roughly 30% of patients with PDD present with a known medical disorder. Seizures are the most frequent comorbidity. Deletions or duplications (eg, 15q duplication) are the most common genetic abnormality associated with PDD.
Autistic disorder is commonly comorbid with intellectual disability. Fragile X syndrome is the most common genetic cause of intellectual disability. Therefore, autistic disorder should be common in those with fragile X syndrome. Several studies have demonstrated an excess of autistic symptom clusters and clinical findings, such as larger head circumference, in individuals with fragile X syndrome greater than would be expected among persons with intellectual disability without a genetic etiology. These features are absent in cases of fragile X syndrome without autism. Therefore, a subtype of fragile X syndrome may be a PDD behavioral phenotype. As evidence mounts that PDDs have biological origins, these genetic syndromes may be used as models to develop new treatment strategies for PDD.
Symptoms of obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) are often present in patients with PDD. Some clinicians label the OCD and ADHD symptoms separately, whereas others include them as part of the presentation of PDD. Regardless of the approach, the symptoms of OCD and ADHD may be disabling and require treatment with standard approaches that include, but are not limited to, medications and behavioral therapy.
Aggression is a symptom not specific to any particular psychiatric disorder. The etiologies are broad and include constipation, depression, anxiety, psychosis, or adjustment disorder. Treatment requires clarification of etiology to help select medications and other appropriate therapies.
Sensory integrations disorder is not found in the DSM-IV or the International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10) but best captures the behavioral problems that result when individuals with PDD become disruptive because they react adversely to loud noises, tags on clothing, or textures of food. They may also be disruptive while trying to seek alternative methods of self-soothing, such as swinging, wrapping themselves in heavy blankets, or eating nonnutritive items. Identification of these sensory needs or deficits is integral to the behavioral management of individuals with PDD.
Regression, or the loss of developmental milestones, was once a controversial finding in autistic disorder. Today, differing degrees of regression are recognized as part of the developmental presentation of autistic disorder. Major losses of developmental milestones suggest Rett Syndrome, childhood disintegrative disorder, or Landau-Kleffner syndrome.
When eliciting history from the parents, reviewing pregnancy, peripartum, and infancy behaviors can yield clues to the genetic etiology of pervasive developmental disorder (PDD) behaviors or support the decision to perform brain imaging. Many parents of children later diagnosed with autism can recall that, as infants, their child had poor eye contact and was unlike older siblings in interpersonal interactions.
Studies using the 1-year birthday party as a developmental milestone show that these children lack interest in the party, do not engage with adults, and/or show inappropriate interest in the gifts or activities. A significant history of neglect or failure to thrive requires consideration of reactive attachment disorder, which is an important differential diagnosis of PDD. If the child has a clinically significant history of physical or emotional deprivation, a diagnosis of PDD should be deferred until the child has had an opportunity to recover in an enriched environment.
A common misconception is that children with a PDD do not show attachment to parent figures. In fact, many children with PDD have an emotional attachment to parental figures, but the attachment may manifest mostly as separation anxiety or as a seeking of comfort in odd ways. Children whose first language is not English may pose additional challenges in differentiating PDD from selective mutism and language disorders.
A thorough medical review is important, because none of the pervasive developmental disorders (PDDs) has a medical cure. Treatable conditions may cause symptoms of PDD, or they may worsen behaviors associated with these disorders.
Any history of deficiencies in the following areas is an indication for an evaluation for PDD:
- Language development
- Social interaction
- Sensory integration
Delay suggests autism or PDD not otherwise specified. Regression is consistent with Rett disorder or childhood disintegrative disorder but may also be an important subtype of autistic disorder. Normal language development is a diagnostic feature of Asperger disorder.
Poor social interaction: Features include the following:
- Social isolation
- Poor eye contact
- Attachment to unusual objects
- Overdeveloped, circumscribed interests in odd or specific topics
- Inability to engage in imaginative play
Sensory integration difficulties: Features include the following:
- Oral aversion to certain textures or colors
- Olfactory aversion
- Tactile aversion to certain fabrics (eg, tags on clothing, position of socks)
- Auditory aversion to loud noises or types of music
Stereotyped behaviors are also an indication for an evaluation for PDD. Such behaviors include hand flapping and self-injurious behavior (eg, head banging). Children with stereotyped behavior may have difficulty making a transition between activities.
Screening for PDD in the pediatric visit
The social communication questionnaire (SCQ) is a short parent report of current and past behavior. It has been validated to be consistent with the Autism Diagnostic Observation Schedule (ADOS) and has excellent sensitivity and specificity for PDDs. The form is filled out by parents of children who are aged 4 years or older and have a mental age of 2 years. It is short enough to be completed in the waiting room.
The Developmental and Behavioral Pediatrics subgroup of the American Academy of Pediatrics recommends using the Modified Checklist for Autism in Toddlers (M-CHAT) Form to screen for symptoms in children aged 16-30 months.
Physical examination findings in children with pervasive developmental disorder (PDD) are usually normal, but the evaluation should be thorough in order to identify genetic or metabolic disorders.
The most important exception is Rett disorder; almost all patients who present with this disorder have the characteristic findings of hand-wringing, hyperventilation, or both. Unlike children with autism, who tend to have larger head circumference (>90%), children with Rett disorder have smaller head circumference (< 10%). Children with fragile X syndrome have a larger head circumference, while children with both fragile X syndrome and autistic disorder have even larger mean head circumference as a group.
Children with PDD often have constipation, diarrhea, or reflux that they may lack the verbal ability to report. Untreated conditions present as disruptive behavior. A physical examination may be the only method to identify these issues. Food allergies may be the etiology of these gastrointestinal issues. Physical findings of eczema, wheezing, and poor weight gain should heighten the suspicion for food allergies.
Psychosis is often the most difficult symptom to elicit and diagnose appropriately in children with pervasive developmental disorder (PDD). Not long ago, children with PDD were often identified as having childhood-onset schizophrenia. The DSM establishes criteria that clearly distinguish PDD from childhood-onset schizophrenia. The DSM recognizes that children with PDD may develop psychotic disorders if they present with clear evidence of auditory, visual, tactile, and/or olfactory hallucinations. Nevertheless, determining whether a child has PDD or psychosis may be difficult during the initial clinical evaluation. For example, individuals with intellectual disability may present with cognitive disorganization; they may link irrelevant thoughts together or have beliefs in magical beings, even as adults. These findings are considered normal in a person with intellectual disability.
Conditions to consider in the differential diagnosis of pervasive developmental disorder, along with those in the next section, include the following:
- Reactive attachment disorder
- Landau-Kleffner syndrome
- Schizotypal personality disorder
- Mental retardation
If the history or physical findings suggest additional concerns, consider the following:
- High-resolution cytogenic studies with fluorescence in situ hybridization (FISH) testing for Prader-Willi, Angelman, and Williams syndromes
- Creatine phosphokinase measurement - To rule out muscular dystrophy
- Determination of lead level - To rule out lead poisoning
- Urine organic acid test
- Plasma amino acid test
- Lactate and/or pyruvate test - To rule out mitochondrial disorders
- Serum ammonia test - To rule out urea cycle defects
- Test for very long fatty acids - To rule out peroxisomal disorders
- Test of thyroid-stimulating hormone - To rule out hypothyroidism
- Gene sequencing for MECP2
A hearing test should be administered. A hearing test should be performed by a pediatric audiologist and should be repeated even if the test results were normal at birth.
Consult a child psychiatrist and/or a developmental/behavioral pediatrician to evaluate and treat comorbid diagnoses such as depression, ADHD, or OCD and to lead a multidisciplinary team for case management, which may include family psycho educational therapy, psychopharmacologic treatment, speech therapy, occupational therapy, physical therapy, and behavioral therapy.
Consult a psychologist and/or an education specialist to assess baseline functions for intellectual capacity and learning disabilities and to design cognitive behavioral strategies for facilitating education and for modifying difficult behaviors. (This area is rapidly growing, with increasing evidence suggesting that specific types of therapy for early intervention can enhance generalization of social skills.)
Additional Patient Management Considerations
Outpatient management requires a multidisciplinary approach. Comorbid medical problems, including seizures and constipation, are frequent. Certain behaviors may require medication prescribed by a child and adolescent psychiatrist or behavioral-developmental pediatrician.
A speech pathologist's expertise is essential to develop a communication plan. The use of augmentative and communication devices is essential for the nonverbal child. A special education professional may be needed to design a specific curriculum for each child with pervasive developmental disorder (PDD).
Occupational and physical therapists may be indicated for motor deficits and sensory processing deficits. A social worker not only helps find financial, educational, and emotional resources but also provides important psychosocial support for the family. Psychologists often develop behavioral plans and ongoing therapy to improve social relationships.