Prenatal Incidental Diagnosis of Turner Syndrome

The authors reviewed baseline data on 88 girls, aged 9 months to 4 years, with karyotype-proven Turner syndrome who were randomized into a multi-center growth hormone trial. The girls were divided by means of diagnosis; 16 were “incidental” (ie, diagnosed by prenatal karyotype performed for advanced maternal age and other reasons unrelated to a suspicion of Turner syndrome) and 72 were “traditional” (ie, diagnosed by karyotype performed for suspicions of Turner syndrome). In the traditional group19 were diagnosed by prenatal karyotype performed because of abnormal ultrasounds, and 53 by postnatal karyotype obtained for clinical findings of Turner syndrome.

The majority of the traditional group (74%) had 45,X chromosomes, whereas the incidental group was mostly (56%) mosaic 45,X/46,XX. Phenotypic features of Turner syndrome occurred more often in the traditional group and in those with the 45,X chromosomes (Figure). The mean length/height was lower in the traditional group (–1.7 + 1.0 versus –1.1 + 1.2 SD), though the difference did not reach significance (P=0.06). Cardiac defects were more common in the traditional group (64% versus 31%), but renal anomalies did not differ.

The authors concluded that the incidental group had a “milder” form of Turner syndrome, thus the phenotypic variability may detract from the prevalence of Turner syndrome as it is likely underestimated. Most prenatal counseling is based on prognostic data derived from “traditionally” diagnosed girls, which may not apply to milder phenotypes and those with mosaic patterns. These differences may be especially important in light of the high rate of elective terminations for fetuses with sex chromosome aneuploidy.

Percentage of patients with phoenotypic features of Turner syndrome subgrouped by method of diagnosis (A) and karyotype (B). A, *P < .05 traditional versus incidental. B, *P < .05 among karyotype groups. *Data combined for features on the left and right.

Editor’s Comment: This paper is a valuable reminder of the phenotypic variability among girls with Turner syndrome. As a corollary, we should not restrict obtaining karyotypes to those girls with “classic” Turner syndrome features. Indeed, a prevalence survey revealed that the only phenotypic features that occurred 100% in Turner syndrome were females with short stature.¹ Delaying or missing the diagnosis has therapeutic sequelae. Not only is the final height outcome better when growth hormone therapy is initiated younger, but initiating growth hormone at a younger age can also obviate the need for delaying puberty in order to prolong time for growth.² A review of the Turner syndrome clinic at University of North Carolina found that short stature was the key to diagnosis in childhood and adolescence, yet there was an average 5.2-year delay to diagnosis from the time the height first fell below the 5^th percentile for age.³ By keeping in mind that Turner syndrome can present with milder phenotypes, we will hopefully improve on this statistic.


Home	Search	Current issue	Archive	Site help
Current GGH - Vol. 24 No. 1 View table of contents Download PDF
Click here to subscribe