Neurodevelopmental and psychosocial aspects of Turner syndrome.

Turner syndrome (TS) is the complex phenotype of human females with complete or partial absence of the second sex chromosome, or monosomy X. A characteristic neurocognitive and psychosocial profile has also been described in TS females. Typically, specific deficits in visual-spatial/perceptual abilities, nonverbal memory function, motor function, executive function, and attentional abilities occur in TS children and adults of varying races and socioeconomic status. TS-associated psychosocial difficulties occur in the areas of maturity and social skills. We hypothesize that a subset of the neurocognitive deficits (visual-spatial/perceptual abilities) are genetically determined and result from abnormal expression of one or more X chromosome genes. In addition, a different subset of these neurocognitive deficits (memory, reaction time, and speeded motor function) result from estrogen deficiency and are at least somewhat reversible with estrogen treatment. The TS-associated psychosocial problems are most likely linked to these core neurocognitive deficits and do not reflect a separate and independent component of the syndrome. Turner syndrome research has progressed significantly over the last decade. The field has moved from descriptive reports based on single individuals or small clinical samples to the use of experimental designs with larger, more diverse and representative samples. This degree of variability among individuals with Turner syndrome in all domains (karyotype or genetic constitution, physical attributes, neurocognitive and social functioning) suggests the need to identify risk and protective factors contributing to the heterogeneity in the phenotype. Active education about TS and participation in patient advocacy groups such as the Turner Syndrome Society of the United States (https://www. turner-syndrome-us.org/) has provided new information for TS adults and families as well as a supportive peer group. MRDD Research Reviews 2000;6:135-141.