Turner syndrome: in Turner syndrome (monosomy X)several reports suggest that the severity of the
phenotype depends on the parent-of origin of the retained X chromosome.
Turner syndrome patients with a maternally retained X (45,Xm) showed significantly
poorer verbal and higher-order executive function skills than those with 45,Xp (Skuse
DH, et al. 1997).
A higher prevalence of cardiovascular abnormalities, neck webbing (Chu
CE, et al. 1994) and autistic disorder has been noted when the retained X was maternal (Donnelly
SL, et al. 2000).
There is also speculation that the X chromosome may encode a paternally expressed locus which
gives a protective effect against autism, explaining the prevalence of autism in males given they
lack paternally inherited X chromosomes (Skuse
L et al (2007) reported that kidney malformations were exclusively found in X(m) patients (P =
0.030); the X(m) group had lower total and low-density lipoprotein cholesterol (P < 0.003), and
higher body mass index sd score (P = 0.030); ocular abnormalities were more common in the paternal X
group (P = 0.017), who also had higher academic achievement.
In contrast, Bondy
CA et al (2007) found no evidence for X-linked genomic imprinting effects on stature or
lymphatic, renal or cardiovascular development in Turner syndrome.
The cognitive phenotype of Turner syndrome involves preservation of verbal skills, and some reports
suggest TS patients may even show superior skills in certain verbal areas compared to controls (Temple
CM and Carney R 1996; Loesch DZ et al, 2005). Superior
temporal gyrus (STG)
morphology (an area of the brain involved
in language capacities) was assessed in 30 TS patients and 30 age matched controls. The right STG
volumes were shown to be significantly larger in TS patients, and differences in STG volumes were
larger in patients with a maternally derived X compared to a paternally derived X chromosome (Kesler
SR et al. 2003).
Among 12 TS patients, the arithmetic IQ scores were significantly poorer in the Xm than in the Xp
AT et al, 2008).
In a study by Hamelin (Hamelin CE et al, 2006) on 54 TS
patients with informative X chromosome inheritance, those with the Xm (n = 26) showed a greater
gain in height as a result of growth
hormone treatment compared to those with Xp (n = 9). In addition, Xp individuals had an increased
prevalence of sensorineural
In a cohort of 33 Korean Turners syndrome patients no differences between Xp and Xm individuals were
observed for cardiovascular and renal defects, and response to GH treatment (Ko
JM et al, 2010). Some maternal effect on height was observed when considering the 20
individuals with 45X only, however replicate cohorts are required.