Diagnostic Criteria

Suggestive Findings

Christianson syndrome (referred to as CS in this GeneReview) should be suspected in an individual with the following clinical manifestations observed in the majority of affected males .

Clinical manifestations

• Developmental delay / intellectual disability (usually severe to profound)

• Absent to minimal language development

• Hyperkinesis

• Epilepsy (onset usually before age three years)

• Truncal ataxia

• Postnatal-onset microcephaly

• Nondysmorphic facial features

Establishing the Diagnosis

The diagnosis of CS is established in a male proband by identification of a hemizygous pathogenic (or likely pathogenic) variant in SLC9A6 and in a female proband by identification of a heterozygous pathogenic (or likely pathogenic) variant in SLC9A6 by molecular genetic testing .

Source: GeneReviews — "Christianson Syndrome"

Differential Diagnosis

Angelman syndrome (AS) is characterized by severe developmental delay or ID, severe speech impairment, gait ataxia and/or tremulousness of the limbs, and a unique behavioral profile with an inappropriate happy demeanor that includes frequent laughing, smiling, and excitability. Microcephaly and seizures are common. Developmental delays are first noted around age six months; however, the unique clinical features of AS do not become manifest until after age one year, and it can take several years before the correct clinical diagnosis becomes apparent. The diagnosis of AS is established in a proband who meets the consensus clinical diagnostic criteria and/or who has findings on molecular genetic testing that suggest deficient expression or function of the maternally inherited UBE3A allele.

Source: GeneReviews — "Christianson Syndrome"

Management Guidelines

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in an individual diagnosed with Christianson syndrome (CS), the evaluations summarized in this section (if not performed as part of the evaluation that led to the diagnosis) are recommended:

• Establishment of baseline neurologic functioning with:

• Assessment of adaptive functioning (e.g., Vineland, Bayley Scales of Infant Development)

• Occupational therapy and physical therapy assessment regarding fine motor and gross motor functioning

• Speech/language/communication assessment

• Assessment of behavioral issues, as needed, using such evaluation tools as Autism Diagnostic Observation Schedule (ADOS) and Autism Diagnostic Interview-Revised (ADI-R)]

• Neurologic examination

• EEG

• Brain MRI (based on the clinician's judgment) to determine if any structural brain abnormalities are present, especially cerebellar / brain stem atrophy

• Evaluation of swallowing function, feeding, and nutrition as needed

• Ophthalmologic assessment, including evaluation for eye movement abnormalities and visual acuity, when warranted

• Consultation with a clinical geneticist and/or genetic counselor

Treatment of Manifestations

Developmental Delay / Intellectual Disability Management Issues

The following information represents typical management recommendations for individuals with developmental delay/ intellectual disability in the United States; standard recommendations may vary from country to country. Ages 0-3 years.

Source: GeneReviews — "Christianson Syndrome"

Surveillance Guidelines

At the time of follow-up clinical examinations, the following are recommended:

• Measurement of weight and height (and calculation of BMI) because of the increased age-related risk for poor weight gain despite normal or even high caloric intake

• Assessment for scoliosis/kyphoscoliosis

• In adolescents / young adults regarding possible regression:

• Evaluation for loss of any of the following: feeding skills, fine/gross motor skills, ambulation, use of words/sounds

• Repeat neuropsychologic assessments (as needed)

• Assessment using an ataxia rating scale

Source: GeneReviews — "Christianson Syndrome"