question: What are the characteristics of Christianson syndrome?
answer: Christianson syndrome (CS) is caused by mutations in the X-linked Na(+) /H(+) exchanger 6 (NHE6). Patients present with prominent neurological, medical, and behavioral symptoms. All CS participants were nonverbal and had intellectual disability, epilepsy, and ataxia. Other neurologic symptoms included eye movement abnormalities (79%), postnatal microcephaly (92%), and magnetic resonance imaging evidence of cerebellar atrophy (33%). Regression was noted in 50%, with recurrent presentations involving loss of words and/or the ability to walk. Medical symptoms, particularly gastrointestinal symptoms, are common. Height and body mass index measures were below normal ranges in most participants. Behavioral symptoms included hyperkinetic behavior (100%), and a majority exhibited high pain threshold.