47, XXY - The Focus Foundation

Myths about 47, XXY (and why they are just myths!)

Testosterone does not influence neurodevelopmental progress in boys with 47, XXY.

Several retrospective studies by Samango-Sprouse et al. [2011, 2013] have shown a positive and sustained treatment effect on all aspects of neurodevelopment when boys with 47, XXY receive early hormonal replacement therapy before 18 months of age.

Boys with 47, XXY are clumsy and not athletic.

Boys with 47, XXY can excel in athletics. Boys with 47, XXY are playing college football, skiing, running cross-country, playing water polo, and are involved with lots of other sports!

Boys with 47, XXY are sterile.

Innovative procedures are now available to extract fertile sperm and preserve for later reproduction.


47, XXY affects as many as 1 in 650 boys, however only 25% are ever diagnosed. X & Y chromosomal aneuploidies are commonly misdiagnosed as ONLY speech or motor delays, leaving millions of affected children undiagnosed.

More than 750,000 people are believed to have X & Y chromosomal variations in the United States alone, with an equal distribution across all racial and socio-economic groups.

Early hormonal replacement therapy (EHRT) is important before 18 months of age. EHRT impacts brain function through at least 9 years of age as evidenced by recent studies.

Boys with 47, XXY consistently present with language-based learning disabilities (LLD) and Motor Planning Issues that are related to the high rate of dyspraxia and dyslexia associated with the disorder. Early speech delay is often a sign of LLD and typically arises by 18 months of age.

Reading dysfunction occurs in 95% of children with 47, XXY. Specific reading programs have been found to be very successful and promote school success and reduce behavioral issues in school.

Boys that are prenatally diagnosed and receive early intervention services typically present less severe and have fewer neurocognitive delays/disabilities.

In the majority of cases the primary cause for dyslexia and dyspraxia is unknown. However, 47, XXY may be the cause in many children.

Related X & Y Disorder Research

X&Y Variation Disorders encompass individuals who are born with 45, 47, 48, or 49 chromosomes, rather than the standard 46. The Focus Foundation’s efforts are centered on disorders resulting from having 47, 48, and 49 chromosomes. 45, X (also known as Turner’s Syndrome) occurs in one out of 2,000 live female births and is actively and effectively served by The Turner Syndrome Society. Below are more details about X&Y Variations involving 47, 48, and 49 chromosomes:

At least 85% of those with 47,XYY are never diagnosed. 47,XYY boys consistently present with language-based Learning Disabilities and difficulties with Motor Planning–both issues that are related to the high rate of dyspraxia and dyslexia associated with the disorder. However, 47,XYY boys are commonly misdiagnosed as simply having speech or motor delays.

Boys with 47,XYY typically reach an average height of between 6’3” and 6’5”…READ MORE

As many as 1 in 900 girls have 47,XXX. Unfortunately, millions of affected girls are undiagnosed. Girls who are prenatally diagnosed and receive early intervention services typically exhibit fewer and less severe cognitive disabilities.

There is an equal distribution of 47,XXX across all racial and socio-economic groups…READ MORE

Boys with 48,XXYY consistently exhibit Language-Based Learning Disabilities (LLD) and difficulties with Motor Planning, issues that are related to the high rate of dyslexia associated with the disorder. However, they seem to be stronger in math and such visual-spatial activities as assembling puzzles or remembering directions.

Intellectual disabilities are common in 48,XXYY, with average full-scale IQs in the range of 70-80. Verbal IQs are seen to be significantly lower than performance IQs, due to language-based learning difficulties…READ MORE

48,XXXX (also known as Tetrasomy X or Tetra X) is a rare sex chromosome disorder that was first identified in the early 1960s. Since that time, approximately 100 cases have been reported, although less than 50 are described in scientific literature. Due to the scarcity of this female chromosomal variation, it is difficult to define a common phenotypic presentation. A lack of congenital malformations, mild dysmorphology, and varied developmental trajectory suggests that 48,XXXX is largely underdiagnosed…READ MORE

48,XXXY can result from meiotic or mitotic nondisjunction (errors in chromosomal separation) and is often considered a variant of Klinefelter syndrome (47,XXY). However, boys with 48,XXXY often exhibit a more complicated neurodevelopmental profile than boys with 47,XXY…READ MORE

The first case of 49,XXXXY syndrome was reported in the 1970s, and this chromosomal variation remains one of the rarest sex chromosome disorders. 49,XXXXY results from nondisjunction (errors in chromosomal separation) of the X chromosome occurring during both Meiosis I and Meiosis II…READ MORE

Penta X Syndrome is an extremely rare chromosomal disorder that only affects females. While girls normally only have two X chromosomes, girls with Penta X have five X chromosomes. As of 2011, less than 40 cases have been reported.…READ MORE

Klinefelter Syndrome & Other Names You May hear

X & Y Variations is a neurogenetic disorder known by many names, among them: Sex Chromosome Disorders, X & Y Chromosomal Variations, Sex Chromosome Anomaly and Sex Chromosome Aneuploidy Variations. Within the disorder are many sub-categories, which are identified by names including 47, XXY (Klinefelter Syndrome), 49, XXXXY, Tetrasomy X, 49, XXXXXX, Pentasomy X, 48, XXY.

What You Can Do Now

If you have received a prenatal diagnosis indicating that your child has an X & Y chromosomal variation, or feel that your son or daughter is experiencing developmental delays or developmental dysfunction, the following options are designed to help you take the next step in securing appropriate treatment or an early diagnosis.


Take The Child Questionnaire



Learn About Chromosomal Microarray

Chromosomal Testing


Syndrome-specific Therapy