Trisomy X

•   Brief Introduction to Trisomy X


•   Proceedings of the 2006 National Conference on Trisomy X and 47,XYY


•   Resources for Individuals and Families Dealing with Trisomy X


•   Read stories about other individuals and families dealing with Trisomy X


•   A Review of Trisomy X (47, XXX)

Brief Introduction to Trisomy X

In 1956, Drs. Joe Tjio and Albert Lavan confirmed that there were 23 pairs of chromosomes in humans.  Up until that time, it had been thought that there were 48 chromosomes, but using a more advanced experimental methodology, Tjio and Lavan were able to confirm that there were, in fact, only 46. (1)  The discovery by Tjio and Lavan is generally considered to be the beginning of modern “cytogenetics,” which is the study of chromosomes and the diseases caused by either numerical and/or structural abnormalities in them.

Because it was thought that all men had 22 pairs of autosomes plus one X and one Y sex-determining chromosomes, they were (and still are) referred to as 46,XY; and because it was thought that all women had the same 22 pairs of automsomes plus two X chromosomes, they were (and still are) referred to as 46,XX.

Three years after Tjio and Lavan’s confirmation of 46 chromosomes in humans, in 1959, a young English researcher named Patricia Jacobs and her associate described the first chromosmal abnormality in man, the extra X chromosome in an estimated 80% of the men with Klinefelter syndrome. (2)  Later than year, Dr. Jacobs identified the extra X in Trisomy X (47,XXX). (3) 

Are women with an extra X chromosome at risk of developing Klinefelter syndrome?

The answer is “No.”  Technically speaking, the name “Klinefelter syndrome” refers to the common set of symptoms described in a 1942 case study prepared by Dr. Harry Klinefelter following his examination of nine adult males being treated for endocrinological disorder. (4)  A number of these symptoms pertain exclusively to males, whereas all Trisomy X individuals are women.  Accordingy, women born with an extra X chromosome are referred to as Trisomy X, Triple X or 47,XXX.

Do 47,XXY and Trisomy X have much in common?

Although there can be broad variability of symptoms, ranging from some persons who are almost entirely asymptomatic to others who are several affected, Trisomy X females and 47,XXY males tend to share a number of common characteristics and challenges. 

According to the latest estimates, the incidence level of Trisomy X is approximately 1 out of 900 live birth females. (5)

(1)  Joe Hin Tjio and Albert Levan, “The Chromosome Number of Man,” American Journal of Obstetrics and Gynecology, 1956, 130:723-724.

(2)  Patricia A. Jacobs and J. A. Strong, “A Case of Human Intersexuality Having a Possible XXY Sex-determining Mechanism,” Nature, 1959, 183: 302-303.

(3)  Patricia A. Jacobs, et. al., “Evidence for the Existence of the Human “Super Female,” Lancet, September 26, 1959, 2:423-5.

(4)  Harry F. Klinefelter, E. C. Reifenstein and Fuller Albright, “Syndrome Characterised by Gynecomastia, Aspermatogenesis with A-Leydigism, and Increased Excretion of Follicle Stimulating Hormone,”  Journal of Clinical Endocrinology, 1942, 2: 615-627.

(5)  [Cite]

Return To Top



Share Your Story

So much of what makes our community wonderful and special is the individuality and uniqueness of each individual’s experience. Our hope is that these stories will help answer important questions that persons who recently received a diagnosis ask concerning these conditions, and set straight a number of the most common misconceptions.

If you would like to contribute your story - and we hope that you will - please send us a Word (.doc) or simple text (.txt) document that is no longer than four type written pages in length including photograph(s) to the .(JavaScript must be enabled to view this email address).  Your story could include tales of victory, struggle, cutest quirks and/or advice to others. If you wish to attain a certain amount of anonymity, you are welcome to avoid using your (or your child’s) full name and town in the materials.  Also, we ask that you not mention the names of specific doctors.

Please accompany your story submission with an executed copy of KS&A’s Standard Consent and Release form whether or not you are including pictures.


Return To Top



A Review of Trisomy X (47, XXX)

Nicole R Tartaglia, Susan Howell, Ashley Sutherland, Rebecca Wilson, and Lennie L. Wilson


Orphanet Journal of Rare Diseases 2010, 5:8doi:10.1186/1750-1172-5-8


Abstract

Trisomy X is a sex chromosome anomaly with a variable phenotype caused by the presence of an extra X chromosome in females (47,XXX instead of 46,XX). It is the most common female chromosomal abnormality, occurring in approximately 1 in 1,000 female births. As some individuals are only mildly affected or asymptomatic, it is estimated that only 10% of individuals with trisomy X are actually diagnosed. The most common physical features include tall stature, epicanthal folds, hypotonia and clinodactyly. Seizures, renal and genitourinary abnormalities, and premature ovarian failure (POF) can also be associated findings. Children with trisomy X have higher rates of motor and speech delays, with an increased risk of cognitive deficits and learning disabilities in the school-age years. Psychological features including attention deficits, mood disorders (anxiety and depression), and other psychological disorders are also more common than in the general population. Trisomy X most commonly occurs as a result of nondisjunction during meiosis, although postzygotic nondisjunction occurs in approximately 20% of cases. The risk of trisomy X increases with advanced maternal age. The phenotype in trisomy X is hypothesized to result from overexpression of genes that escape X-inactivation, but genotype-phenotype relationships remain to be defined. Diagnosis during the prenatal period by amniocentesis or chorionic villi sampling is common. Indications for postnatal diagnoses most commonly include developmental delays or hypotonia, learning disabilities, emotional or behavioral difficulties, or POF. Differential diagnosis prior to definitive karyotype results includes fragile X, tetrasomy X, pentasomy X, and Turner syndrome mosaicism. Genetic counseling is recommended. Patients diagnosed in the prenatal period should be followed closely for developmental delays so that early intervention therapies can be implemented as needed. School-age children and adolescents benefit from a psychological evaluation with an emphasis on identifying and developing an intervention plan for problems in cognitive/academic skills, language, and/or social-emotional development. Adolescents and adult women presenting with late menarche, menstrual irregularities, or fertility problems should be evaluated for POF. Patients should be referred to support organizations to receive individual and family support. The prognosis is variable, depending on the severity of the manifestations and on the quality and timing of treatment.

To download the full article, go to the Orphanet Journal of Rare Diseases

Click here to read a personal dedication from co-author, Lennie Wilson
Return To Top