Endocrine, cytogenetic and psychometric features of patients with X-isochromosome 46, X, i(Xq) Turner's syndrome: a preliminary study in nine patients.

The 46, X, i(Xq) karyotype of isochromosome for the long arm of the X chromosome has been found to be a frequent structural abnormality in Turner's syndrome. To characterize the endocrine, metabolic, and psychometric features of such patients, nine subjects, aged 12 to 49 years, with this specific cytogenetic abnormality were studied. Although eight of the nine patients had a mosaic chromosome pattern, five had a greater proportion of i(Xq) cells than XO cells, and in four of these the proportion of i(Xq) cells was over 80%. Eight of the nine isochromosomes were metacentric and most had a single C-band. Two subjects were hypothyroid, six had thyroid antibodies present and five had parietal cell antibodies. Oral glucose tolerance testing was abnormal in three and elevated insulin levels were present in an additional two subjects. Psychometric testing showed some discrepancy between verbal and performance I.Q. scores, the performance scores generally being lower. Thus, thyroiditis, insulin insensitivity and diabetes mellitus, parietal cell antibodies, and a relatively low performance I.Q. are found in some of the 46, X, i(Xq) Turner's syndrome patients. The highest thyroid antibodies were present in the four subjects in whom more than 80% of cells were 46, X, i(Xq). Two of these subjects also had diabetes mellitus and three had antiparietal cell antibodies. These findings suggest an association of autoimmune disease with this particular cytogenetic abnormality.