A developmental study of girls with trisomy X.

Development of 11 girls (ages 2-10 years) with 47,XXX karyotype identified in a newborn survey is compared with eight girls having a mosaic sex chromatin pattern and with the normal siblings of each group. Delay in early motor development and speech, a mild intellectual deficit, and disturbance in interpersonal relationships occurred in one-third of the index cases, a higher frequency than in the comparison groups. two-thirds were considered normal and adequately adjusted. No consistent phenotype was found.