The Differential Diagnosis of Childhood Developmental Disorders

• It is difficult to categorize psychopathological symptoms consistent with developmental disorders into discrete groups, such as organic or functional.
• Long-term outcomes for children with symptoms that suggest a severe developmental disorder are difficult to predict.

A case vignette provides a concrete example of these issues.

Case Vignette

JB is a 14-year-old African American boy with Down syndrome, moderate intellectual disability, complex partial seizures, and sickle cell disease. He presents with a sudden onset of increased aggression, irritability, and self-injury 1 to 2 weeks after hospitalization for a sickle cell crisis. He experienced both severe pain and a cerebrovascular accident that resulted in apparent nonfluent aphasia, right-sided hemiparalysis, and a flurry of seizure activity. JB’s neurologist increased the dosage of levetiracetam, an anticonvulsant. Neurological imaging revealed a recent subcortical infarction in his left prefrontal cortex and caudate nucleus. He was referred to his primary care physician for depression 6 weeks after his hospitalization. She prescribed 20 mg of fluoxetine daily. Unfortunately the SSRI was associated with increased agitation, which the primary care doctor thought was drug-induced mania. The drug was withdrawn and the agitation abated. The patient was referred to a psychiatrist.

The differential diagnosis

Although an extreme example, this case illustrates the complexity of assessing children with developmental disorders. As with most referrals, this one also focused on an exacerbation of preexisting challenging behaviors. The primary care physician diagnosed depression but was alarmed by a sudden onset of what she felt was medication-induced mania and referred JB for a psychiatric evaluation.

Before embarking on a differential diagnosis for JB, several fundamental premises needed to be considered. A subset of developmental disorders, intellectual disability represents impairment in cognitive and adaptive skills. These deficits increase vulnerability to environmental changes and heighten the likelihood of intense, negative emotional reactions to these circumstances. Catastrophic reactions can be misattributed to mood disorders, or they may evolve into chronic conditions in the face of persistent stressors as when target behaviors (especially escape behaviors) are reinforced by significant others.¹

Mood disorders are common in persons with Down syndrome. The differential diagnosis of depressive disorders requires ruling out thyroid disorders, sleep-related breathing disorders, folate and B₁₂ deficiency, and the early phases of Alzheimer-like dementia.^2,3 The presence of a chronic relapsing disorder such as sickle cell disease increases the risk for mood disorders (because of chronic pain, multiple hospitalizations, and limits on psychosocial development).⁴

Mood disorders develop in up to 40% of patients within a year after a cerebrovascular accident. Individuals who have had a left frontal-striatal stroke are vulnerable to both increased irritability and catastrophic reactions, as well as other symptoms consistent with major depressive disorders.⁵ Complex partial seizures are both predisposing and precipitating factors for mood disorders. Depressive disorders are more common among individuals with frequent complex partial seizures. This relationship is probably the result of compromised limbic function secondary to refractory seizures. Adverse effects from several anticonvulsants can also seriously limit social, academic, and occupational adjustments and contribute to this problem.⁶

The process of differential diagnosis begins by asking which of these factors contributed to the abrupt increase in JB’s agitation, explosive-aggressive behavior, and self-injurious behavior? The answer requires collecting detailed descriptions of his target symptoms from multiple sources and integrating medical and neurological information, psychological reports, functional behavioral analyses, and evidence from the psychiatric mental status examination. Once this information is gathered, the differential diagnosis follows a decision algorithm outlined in Table 2.