Turner's syndrome and variations of Turner's syndrome including “mixed” gonadal dysgcnesis may be viewed as members of a single group of disorders, the gonadal dysgeneses. Seven patients are described whose various clinical and cytogenetic features make them represcntative of the many individuals with one of the gonadal dysgeneses reported from other clinics. The developmental abnormalities which occur, including dysgenetic gonadal tissue, may be traced to the presence during embryonic life of a monosomic (45, X) or a genetically deficient (e.g., 46, XXqi) cell line, whereas a degree of normal gonadal development in some individuals may he traced to the presence also of normal female or male cells.
A unifying explanation for these disorders is presented in terms of a single erroneous chromosomal event occurring after fertilization. Such an event may well be an intrachromosomal rearrangement affecting either an X or a Y, from which may derive a cell line containing a structurally abnormal sex chromosome, a monosomic cell line, or both. The preponderance of affected individuals showing non‐mosaic monosomy (45, X), or the mosaic combination of monosomic cells with cells having a structurally rearranged X or Y chromosome, points to the zygote as the cell in which the disruptive event occurs most often. The less frequent co‐existence of normal diploid cells with abnormal (monosomic or deficient) cells indicates that the disruptive event sometimes occurs in an early postzygotic cell.