The 9q Subtelomeric Deletion Syndrome (9qSTDS) is clinically characterized by mental retardation, childhood hypotonia, and facial dysmorphisms. Haploinsufficiency of the EHMT1 gene has been demonstrated to be responsible for its core phenotype. In a significant number of patients behavioral abnormalities like aggression, impulsivity, and chaotic behaviors are present as well as epileptic phenomena. Reports about the developmental, behavioral, and neuropsychiatric aspects of 9qSTDS are scarce and mostly limited to young patients only. In this report, the behavioral and neuropsychiatric characteristics of one male and one female middle-aged patient are described in whom the genetic diagnosis, interstitial and telomeric 9q deletion, respectively, was established recently. In both patients a remarkable sleep disturbance, characterized by frequent awakenings and daytime sleepiness, was present as well as a prominent apathy syndrome. The observedmotor signs such as rigid flexure of the arms and finger stereotypies persisted over a period of many years and could therefore not be viewed as symptoms of catatonia. It is concluded that the proposed behavioral phenotype of 9qSTDS comprises at least an erratic sleep pattern and an enduring severe apathy.

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American Journal of Medical Genetics. Part B: Neuropsychiatric Genetics
Erasmus MC: University Medical Center Rotterdam

Verhoeven, W., Kleefstra, T., & Egger, J. (2010). Behavioral phenotype in the 9q subtelomeric deletion syndrome: A report about two adult patients. American Journal of Medical Genetics. Part B: Neuropsychiatric Genetics, 153(2), 536–541. doi:10.1002/ajmg.b.31015