Trisomy X syndrome, or 47, XXX, develops in approximately 1 in 1000 girls but is yet to be diagnosed in many patients. The cause remains unknown, and various physical, intellectual, motor, cognitive and hormonal features may be encountered, although an asymptomatic course is common. The diagnosis can be made either prenatally or postnatally through chromosomal analysis.
The clinical course of trisomy X syndrome is variable, with many girls and women being asymptomatic from birth and throughout childhood  . This may be one of the reasons why estimates suggest that only 10% of individuals having this mutation are clinically diagnosed . However, numerous features are encountered in different age periods    :
It is important to mention that structural organ abnormalities of the kidney (unilateral kidney and renal dysplasia) and the heart (atrial or ventricular septal defects, coarctation of the aorta and pulmonic stenosis) have been observed in a small, but a significant portion of patients  .
The diagnosis of trisomy X syndrome can be difficult to make if symptoms are mild or even absent, which is commonly the case. However, the physician must develop clinical suspicion toward this frequently undiagnosed syndrome in the setting of tall stature that is not supported by parental height, intellectual or psychosocial symptoms, and the presence of other typical features. For this reason, a detailed patient history, and physical examination are the most important parts of workup that will enable the physician to make a presumptive diagnosis. Increased maternal age (estimated around 33 years) is commonly observed in children who subsequently develop trisomy X syndrome, and further information regarding birth weight, as well as growth and development of girls throughout childhood by parents can be of essential importance . Because several genitourinary and cardiac structural diseases have been diagnosed in trisomy X patients, ultrasonography of the abdomen and heart, respectively, should be performed. Moreover, magnetic resonance imaging (MRI) of the brain and electroencephalography (EEG) are recommended during workup, but apart from a reduced brain volume, they yield normal findings in virtually all patients  . Genetic studies are necessary to make the diagnosis . Analysis of the karyotype in cells will show an additional X chromosome, and the same finding can be identified prenatally when chorionic villus sampling (CVS) or amniocentesis can detect changes in the number of chromosomes  .