Turner Syndrome with Ring X Chromosome: Do They Have a Distinct Phenotype?

Abstract

In contrast to classic Turner syndrome, Turner patients with ring X chromosome are associated with distinct dysmorphism and are likely to be mentally impaired. Four Turner patients with ring X chromosome were examined for phenotypic features of Turner syndrome and additional dysmorphism. Both patients 1 and 2 are twins with normal intelligence whereas patients 3 and 4 have mental impairment. With the exception of patient 4, the other three patients only have few Turner characteristics. None of the patients have the distinctive dysmorphism previously reported in Turner syndrome with ring X chromosome. Both twins developed spontaneous puberty. Patients 3 and 4 however had no spontaneous puberty. We postulate that this variation may be related to the ring size, the proportion of 45,X and ring X chromosome in cell lines of various body tissues as well as the ability of these rings to be inactivated as a result of lyonisation.

A short girl with learning disability due to Turner mosaicism with a ring X chromosome

“…Females with Tuner mosaic with a ring X chromosome karyotype can have the characteristic features of TS including short stature, cubitus valgus, ovarian dysgenesis, and thyroid disorders 4,5 . Lack of certain other TS features, such as neck webbing and early life lymphoedema is reported in this rare genotype, and were also absent in our patient 6 .…”

“…However, there is a lack of data on growth hormone utilisation in girls with Turner mosaicism with ring X chromosome. Spontaneous puberty and menarche has been reported in two girls, who later required female hormone replacement therapy in young adulthood 6 .…”