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Conditions We See

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The eXtraordinarY Kids Clinic is a unique multidisciplinary clinic that addresses the medical, developmental, and psychological needs of children or adolescents with X&Y chromosome variations. After a clinical evaluation, families receive a comprehensive report detailing specific recommendations for the child based on their condition and assessment in order to support the child’s developmental, academic and emotional needs, as well as medical management. Developmental assessments for infants and children with a prenatal diagnosis are provided. Patients in the clinic are also followed for medication management if needed.
What are X&Y Chromosome Variations?
X&Y chromosome variations are commonly diagnosed from a blood test called a karyotype and the results show that the individual has an additional X and/or Y chromosome. These conditions, depending on the result, can occur in males or females. Examples of X&Y chromosome variations include:
  • 47,XXY (Klinefelter Syndrome)
  • 47,XXX (Triple X, Trisomy X, Triplo X)
  • 47,XYY
  • 48,XXYY
  • 48,XXXY
  • 48,XXXX (Tetrasomy X)
  • 49,XXXXY
  • 49,XXXXX (Pentasomy X)

To learn more about the features of these conditions or how to obtain genetic testing to determine if you or your child has an X&Y chromosome variation, visit our frequently asked questions page.


X&Y chromosome variations refer to conditions in which a child has an abnormal number of sex chromosomes, also known as X&Y chromosomes. Other words used to describe X&Y chromosome variations are “sex chromosome anomaly,” “sex chromosome abnormality” and “sex chromosome aneuploidy.”

Males usually have one X and one Y chromosome, and females usually have two X chromosomes. Occasionally, because of problems with the formation of a parent’s sperm or egg, a child can be born with extra or too few sex chromosomes.

For reasons we don’t completely understand, children with X&Y chromosome variations can also have developmental delays, learning disabilities and social-emotional difficulties. Babies diagnosed prenatally or during infancy with an X&Y chromosome variation should be monitored closely during early developmental years (birth to 5), including standardized developmental assessments to determine if early interventions are needed. Children with an X&Y chromosome variation should have neuropsychological testing during early academic years to monitor for learning disabilities, attentional problems, and social/emotional concerns. Boys with extra X chromosomes need to be seen by an endocrinologist during puberty to help monitor their testosterone levels. Girls who are missing an X chromosome (Turner syndrome) also need ongoing monitoring and treatment by endocrinology, cardiology, and other specialties.

Specific forms of sex chromosome variations include: **TABLE GOES HERE**




Males with an extra X chromosome (XXY/Klinefelter Syndrome, XXYY, XXXY, etc). need care from an endocrinologist, a specialist in hormones, who will monitor for the need for testosterone treatment starting in puberty. This is because the extra X chromosomes usually lead to small testicles and a testosterone deficiency that delays or prevents full pubertal development.

Characteristics of XXY
  • Speech delays more prominent than motor delays
  • Problems with fine & gross motor coordination, fine motor dexterity
  • Normal IQ, lower verbal
  • Language-based learning disabilities
  • Reading problems/Dyslexia
  • 80% needed special education assistance in school
  • Shyness, social withdrawal
  • Testosterone deficiency
  • Low body hair
  • Little or no acne
  • Little or no testicular enlargement
  • Persistent gynecomastia (male breast development)
  • Tall stature



XYY syndrome is a genetic condition that occurs when a male has an extra copy of the Y chromosome in each of their cells (XYY). Sometimes, this mutation is only present in some cells. Males with XYY syndrome have 47 chromosomes because of the extra Y chromosome.

This condition is also sometimes called Jacob’s syndrome, XYY karyotype, or YY syndrome. According to the National Institutes of Health, XYY syndrome occurs in 1 out of every 1,000 boys.

For the most part, people with XYY syndrome live typical lives. Some may be taller than average and face learning difficulties or speech problems. They may also grow up with minor physical differences, such as weaker muscle tone. Besides these complications, though, males with XYY syndrome don’t usually have any distinguishing physical features, and they have normal sexual development.

Symptoms in a baby who has XYY syndrome can include:

  • hypotonia (weak muscle tone)
  • delayed motor skill development, such as with walking or crawling
  • delayed or difficult speech

Symptoms in a young child or teenager with XYY syndrome can include:

  • an autism diagnosis
  • attention difficulties
  • delayed motor skill development, such as with writing
  • delayed or difficult speech
  • emotional or behavioral issues
  • hand trembling or involuntary muscle movements
  • hypotonia (weak muscle tone)
  • learning disabilities
  • taller-than-average height

In adults, infertility is a possible symptom of XYY syndrome.