Kaplan + Sadock's Synopsis of Psychiatry, 11e

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Chapter 31: Child Psychiatry

Available data indicate a prevalence of 6 to 7 cases of Rett syndrome per 100,000 girls. Originally, it was believed that Rett syndrome occurred only in females, but males with the disorder or syndromes that are very close to this disorder have now been described. Rett syndrome is not fully included within autism spectrum disorder, and if present along with autism spectrum disorder it should be diagnosed as an associated disorder. Etiology.  The cause of Rett syndrome is unknown, although the progressive deteriorating course after an initial normal period is compatible with a metabolic disorder. In some patients with Rett syndrome, the presence of hyperammonemia has led to postulation that an enzyme metabolizing ammonia is defi- cient, but hyperammonemia has not been found in most patients with Rett syndrome. It is likely that Rett syndrome has a genetic basis. It has been seen primarily in girls, and case reports so far indicate complete concordance in monozygotic twins. Diagnosis and Clinical Features.  During the first 5 months after birth, infants have age-appropriate motor skills, normal head circumference, and normal growth. Social inter- actions show the expected reciprocal quality. At 6 months to 2 years of age, however, these children develop progressive encephalopathy with a number of characteristic features. The signs often include the loss of purposeful hand movements, which are replaced by stereotypic motions, such as hand-wring- ing; the loss of previously acquired speech; psychomotor retar- dation; and ataxia. Other stereotypical hand movements may occur, such as licking or biting the fingers and tapping or slap- ping. The head circumference growth decelerates and produces microcephaly. All language skills are lost, and both receptive and expressive communicative and social skills seem to pla- teau at developmental levels between 6 months and 1 year. Poor muscle coordination and an apraxic gait with an unsteady and stiff quality develop. Associated features include seizures in up to 75 percent of affected children and disorganized EEG findings with some epi- leptiform discharges in almost all young children with Rett syn- drome, even in the absence of clinical seizures. An additional associated feature is irregular respiration, with episodes of hyperventilation, apnea, and breath holding. The disorganized breathing occurs in most patients while they are awake; dur- ing sleep, the breathing usually normalizes. Many patients with Rett syndrome also have scoliosis. As the disorder progresses, muscle tone seems to change from an initial hypotonic condi- tion to spasticity to rigidity. Although children with Rett syndrome may live for well over a decade after the onset of the disorder, after 10 years, many patients are wheelchair-bound, with muscle wasting, rigid- ity, and virtually no language ability. Long-term receptive and expressive communication and socialization abilities remain at a developmental level of less than 1 year.

Her development during the first months of life was unremark- able. At approximately 8 months of age, her development seemed to wane, and her interest in the environment, including the social environment, declined. Dana’s developmental milestones failed to progress, and she became markedly delayed; she was just starting to walk at her second birthday and had no spoken language. Evaluation at that time revealed that head growth had decelerated. Self-stim- ulatory behaviors emerged, and in addition, marked cognitive and communicative delays were noted on formal testing. Dana began to lose purposeful hand movements and developed unusual stereotypi- cal hand-washing behaviors. By age 6, her EEG was abnormal and abnormal hand movements were prominent. Subsequently, Dana developed truncal ataxia and breath-holding spells, and motor skills further deteriorated. (Adapted from Fred Volkmar, M.D.) Differential Diagnosis.  Rett syndrome shares some fea- tures with autism spectrum disorder; however, the two disorders have some predictable differences. In Rett syndrome, there is deterioration of developmental milestones, head circumference, and overall growth, whereas in autism spectrum disorder, aber- rant development is usually present from early on. In Rett syn- drome, specific and characteristic hand motor movements are always present; in autism spectrum disorder hand mannerisms may or may not appear. Poor coordination, ataxia, and apraxia are predictably part of Rett syndrome; however, individuals with autism spectrum disorder may have unremarkable gross motor function. In Rett syndrome, verbal abilities are usually lost com- pletely, whereas in autism spectrum disorder language is widely variable from markedly aberrant to relatively mildly impaired. Respiratory irregularity is characteristic of Rett syndrome, and seizures often appear early. In autistic disorder, no respiratory disorganization is seen, and seizures do not develop in most patients; when seizures do develop, they are more likely in ado- lescence than in childhood. For autism spectrum disorder that is associated with another neurodevelopmental disorder such as Rett syndrome, the latter disorder is diagnosed in association with autism spectrum disorder. Course and Prognosis.  Rett syndrome is progressive, and those individuals who live into adolescence and adulthood func- tion at a cognitive and social level equivalent to that in the first year of life. Treatment.  Treatment is symptomatic. Physiotherapy has been beneficial for the muscular dysfunction, and anticonvulsant treatment is usually necessary to control the seizures. Behavior therapy, along with medication, may help control self-injurious behaviors, as it does in the treatment of autistic disorder, and it may help regulate the breathing disorganization. Childhood Disintegrative Disorder The previous diagnosis of childhood disintegrative disorder, now included in autism spectrum disorder, is characterized by marked regression in several areas of functioning after at least 2 years of apparently normal development. Childhood disinte- grative disorder, also called Heller’s syndrome and disintegra- tive psychosis, was described in 1908 as a deterioration over

Dana was born as a full-term and healthy baby term after an uncomplicated pregnancy. An amniocentesis had been obtained because of advanced maternal age of 40 years, and findings were normal. At birth, Dana received good Apgar scores and her weight, height, and head circumference were all near the 50th percentile.