The Differential Diagnosis of Childhood Developmental Disorders

Making a diagnosis

Table 2 provides ample evidence for the multifactorial etiology of mental disorders in children with developmental disorders. The most parsimonious Axis I diagnosis is mood disorder due to medical conditions in the context of severe profound intellectual disability, sickle cell disease, cerebrovascular accident, complex seizure disorder, or Down syndrome. As discussed earlier, each of these medical conditions affects mood and illustrates the problem clinicians face in differentiating organic from functional psychiatric disorders in this population. The exacerbation of JB’s self-injurious behavior and aggression is probably related to mood changes and provides an example of the concept of baseline exaggeration.

General challenges

The assessment of psychiatric disorders is often limited by social and communication deficits, sensory impairments, as well as neurological and genetic/metabolic disorders. Because of these challenges, it is difficult to obtain sufficient data to define subtypes of mood disorders. In many situations, we are missing data that help establish the age at onset, pattern of onset, longitudinal course, severity and/or polarity, and other comorbid psychiatric disorders. Yet in spite of these diagnostic limitations, the prevalence rate of diagnosed psychiatric disorders in children with developmental disorders exceeds that of the general population.¹

For clinicians the presence of behavioral phenotypes associated with specific genetic disorders can confound the differential diagnosis of psychiatric diagnosis. Problems arise because symptoms associated with several of these behavioral phenotypes overlap those of many psychiatric disorders. For example, persons with fragile X syndrome display social anxiety and gaze aversion that resemble autism. Variations in the dopamine DA4 receptors affect temperamental traits such as novelty seeking and risk-taking. For others, different alleles for specific genes regulating serotonin transporter proteins increase the risk for stress-induced mood and posttraumatic stress disorders. These gene-behavior relationships differ from the polygenic inheritance and complex behavioral symptoms associated with primary psychiatric disorders.^7,8 Teasing out the nature of these relationships can permit clinicians to define subtypes of self-injurious behavior or aggression that might predict treatment response. A similar case can be built for differentiating specific endophenotypes of major psychiatric disorders.

The coexistence of autism spectrum disorders can also complicate things. For example, unwary clinicians can misattribute odd social behaviors during an interview as a manifestation of a severe mental disorder rather than a pervasive developmental disorder. Another clinician may elicit symptoms of severe mental illness but misattribute them as being “normal” for individuals with autism spectrum disorders (ie, all people with autism behave this way). A more insidious problem involves patients referred for medication management of mood or psychotic disorders without a differential diagnosis. The referring clinician cut short the differential diagnosis and made a provisional diagnosis based on a single symptom (eg, crying, sadness, insomnia, or hallucinations). Conversely, children are referred with a list of target symptoms but without additional data (sleep, mood, or social interests) that would assist in making a primary psychiatric diagnosis.^1,9

Clinicians who successfully negotiate the differential diagnosis gauntlet still run into problems fitting the child into existing diagnostic criteria. The publication of the Diagnostic Manual for Intellectual Disabilities (DM-ID) represents a step toward resolving this problem.¹⁰ Although not yet validated by extensive field trials and statistical analysis, the DM-ID provides descriptive categorical criteria modified to accommodate across the spectrum of intellectual disabilities. But there are remaining problem areas. As the case vignette demonstrates, there is still considerable etiological diversity and clinical heterogeneity within psychiatric disorders. This diversity should remind us that most psychiatric disorders represent a final common pathway for multidirectional abnormalities of brain development and maturation.¹⁰

Conclusion

Determining a differential diagnosis is a process in which inclusion and elimination are used to narrow a range of presenting symptoms into a psychiatric disorder. However, because most child psychiatry referrals result from problematic behavior, the goal of melding these behaviors with diagnostic questions can be overlooked for children with potential developmental disorders. As a result, and as with much of child psychiatry, the differential diagnosis often involves translating target behaviors into symptoms. The diagnosis then results from synthesizing these data from multiple sources.

Ideally, behavioral specialists, mental health providers, family members, group home staff, primary care physicians, neurologists, and geneticists all contribute to a better understanding of the possible etiological and therefore diagnostic impressions in these complicated patients. The result of this synthesis is a biopsychosocial understanding of a child’s symptoms. Ultimately, this is the most effective means by which therapeutic guidelines can be developed. The work is by definition multidisciplinary and multisystemic, providing a true model for the collaborative care that children with developmental disorders need and deserve.

With increasing focus on community-based services for children with intellectual disabilities (IDs), it is quite likely that many psychiatrists will be called on to assess children and adults with ID and mental disorders. For many clinicians in the field, it is readily apparent that there is a dearth of treatment resources in many communities for patients with ID. There are even fewer resources for those with dual diagnoses. The American Association of Intellectual Disabilities has state and local branches that can provide referral assistance for individuals with ID. The National Association of Dual Diagnosis is an organization of professionals with expertise in both ID and mental disorders. Both organizations have Web sites that provide lists of providers. State Departments of Mental Health and Developmental Disability provide local services but all to often services are segregated in separate agencies.