Christianson syndrome

Christianson syndrome is an X-linked neurodevelopmental condition caused by a disease-causing variant in SLC9A6, which encodes the endosomal sodium-hydrogen exchanger NHE6. It was first described in a South African family, but it has since been identified in families from many countries and is not limited to a particular ancestry or location.1

At a glance

• Cause: A pathogenic or likely pathogenic SLC9A6 variant.1
• Inheritance: X-linked. Some variants are inherited and some arise de novo; family testing and recurrence counseling require a genetics professional.1
• Typical presentation in males: Developmental delay or intellectual disability, absent or limited speech, postnatal microcephaly, seizures, ataxia or an unsteady gait, and hyperactivity or frequent smiling and laughter.1
• Females: People with one altered SLC9A6 copy can be unaffected or can have learning, behavioral, or other neurodevelopmental features. “Carrier” does not mean “always asymptomatic.”1

Diagnosis

The diagnosis is established by identifying a pathogenic or likely pathogenic SLC9A6 variant that explains the clinical findings. A variant of uncertain significance does not confirm or exclude the diagnosis. Testing may use a neurodevelopmental or epilepsy gene panel with deletion/duplication analysis, or exome or genome sequencing; the appropriate method depends on the individual's history and prior results.1

Clinical course and care

The course is variable and published natural-history data remain limited. Feeding and swallowing difficulty, poor growth, reflux, sleep concerns, eye-movement abnormalities, scoliosis, and loss of previously acquired motor, feeding, or communication skills have been reported. These findings are not universal, and a small case series should not be used to predict one person's future.1

There is currently no established disease-modifying treatment. Care treats the person's manifestations and may involve neurology, genetics, gastroenterology or nutrition, rehabilitation, ophthalmology, primary care, and school or community services. Anti-seizure treatment, feeding support, sleep care, and mobility or orthopedic management should be selected from the person's findings rather than a syndrome-wide drug or diet list.1

Seek prompt clinical review for new seizures, loss of skills, choking or recurrent respiratory symptoms, significant weight change, new weakness, or a change in walking.

Communication and AAC

Many affected males have minimal speech, but communication ability and access needs must be assessed individually. Document and support all meaningful communication, including vocalizations, facial expression, body movement, gesture, signs, objects, pictures, spelling, and speech-generating technology.

An AAC assessment should consider:

• what the person understands and how they currently express choice, refusal, pain, comfort, and social connection;
• ataxia, tremor, fatigue, positioning, seizure recovery, and changes across the day;
• vision, eye-movement findings, hearing, and symbol or literacy access;
• direct touch, keyguards, switches, partner-assisted scanning, or eye gaze based on observed performance—not diagnosis;
• partner training, access in every setting, and a low-tech backup.

AAC has no cognitive or age prerequisite and should remain available alongside speech, gesture, sign, and other effective modes.3 For the generic evaluation, trial, funding, and implementation process, use the AAC device acquisition guide.

Coding and identifiers

• Gene: SLC9A6 (Xq26.3).
• OMIM phenotype: 300243, intellectual developmental disorder, X-linked, syndromic, Christianson type.

No syndrome-specific ICD-10-CM code is established in the sources reviewed here. Coding should reflect the documented diagnoses and manifestations under the current local coding system. Do not use a muscle-disorder code solely because Christianson syndrome can affect movement.1

Sources

1. Morrow and Pescosolido. Christianson Syndrome, GeneReviews — diagnosis, inheritance, clinical features, management, surveillance, and identifiers; revised September 18, 2025.
2. Pescosolido et al. Genetic and phenotypic diversity of NHE6 mutations in Christianson syndrome — multicenter phenotype and genotype series (2014; PMID 25044251).
3. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — individualized, multimodal AAC assessment and no-prerequisite guidance.

Review boundary

This guide supports discussion and care planning; it does not diagnose Christianson syndrome or prescribe treatment. A genetics or neurology clinician should interpret variants, seizures, regression, and surveillance for an individual. Feeding and AAC plans should be reviewed by clinicians who can directly assess swallowing, communication, motor access, and vision.