XYY SYNDROME

Background
Medical Management Considerations
References
Resources for Families
Advisory Committee
Publication Information

Learning Points

  • Confirm that XYY syndrome is the condition in which males have two Y chromosomes and the chromosome constitution 47, XYY rather than the usual one Y chromosome.
  • Recognize that newborn boys with XYY exhibit no special physical stigmata except for increased height.
  • Restate the occurrence of XYY Syndrome (1:1,000 men).
  • List five characteristic features of XYY Syndrome; e.g.,
    • Developmental delay and/or behavior problems
    • Average final height approximately 7 cm above average
    • Normal body build
    • Comparatively low weight relative to stature
    • Larger craniofacial dimensions than in non-XYY males
  • Delineate two ongoing medical management considerations for XYY males in late childhood, 5-13 years); e.g.,
    • Monitor for learning problems, refer as necessary
    • Continue to encourage that excess physical energy be channeled into play, sports or other physical activities
  • Refer families to appropriate resources on XYY Syndrome.

BACKGROUND
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Description and Causes

XYY syndrome is the condition in which males have two Y chromosomes and the chromosome constitution 47,XYY rather than the usual one Y chromosome. Discovered in 1961 by Sandberg and co-workers, newborn boys with XYY exhibit no special physical stigmata except for increased height. No definite causes of the chromosome aberration have been identified.

Boys with XYY syndrome often are more physically active than other males. If this activity is channeled into play, sports or other physical activities, this fact is in no way negative. Boys with XYY syndrome have a tendency to delayed mental maturation and an increased tendency for learning problems in school.

XYY boys commonly develop normally in childhood, and their intelligence is usually within the normal range. Their increased growth velocity is evident during the earliest childhood.

Physical sexual development is normal, with normal development of sex organs and of secondary sex characteristics. Puberty appears at the expected time, and XYY males are fertile in spite of somewhat decreased sperm quality with many “immature” sperm cells.

XYY males do not demonstrate an increased risk of diseases in childhood or adulthood. Very rarely are sons of XYY males XYY themselves.

Diagnosis

Karyotyping can confirm XYY syndrome; however, XYY males neither look nor behave in a manner which would prompt testing for chromosome abnormality. The most common indication for an XYY male to be karyotyped will be developmental delay and/or behavior problems. Generally diagnosed when prenatal karyotyping is done for the detection of Down syndrome and other major aneuploidies, most XYY males will go through life without being karyotyped.

Occurrence

  • 1:1,000 men

Characteristic Features

  • Most common indicators are developmental delay and/or behavior problems
  • Average final height approximately 7cm above average
  • Normal body build
  • Comparatively low weight relative to stature
  • Larger craniofacial dimensions than in non-XYY males
  • Severe acne in adolescence

Common Associations

Several case reports suggest an association between XYY syndrome and renal agenesis or cystic dysplasia of the kidney leading to Potter sequence (Rudnick-Schoneborn et al. 1996).

Some support for hypothesis that a loss of balance of gene products on the sex chromosomes, possibly including XYY syndrome, may predispose affected individuals to susceptibility to additional genetic and environmental insults that result in childhood-onset psychotic disorders (Kumra et al. 1998).

MEDICAL MANAGEMENT CONSIDERATIONS
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Note: These considerations are in addition to the normal medical care provided to an individual without XYY syndrome. All recommendations can be addressed through clinical examination by the primary care provider, unless otherwise noted.

Ongoing

  • Recommend that excessive physical activity be appropriately channeled

Infancy of Early Childhood (Birth to 5 years)

  • Refer to speech therapist if speech development is delayed
  • Check that child receives early and adequate stimulation to appropriately channel excess physical energy

Late Childhood (5 to 13 years)

  • Monitor for learning problems, refer as necessary
  • Learning problems, not found in all XYY males, are most pronounced during the first years of school
  • Continue to encourage that excess physical energy be channeled into play, sports or other physical activities

Adolescence and Adulthood (13 years and over)

  • Check that excess physical energy is appropriately channeled

REFERENCES
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Peer-reviewed Journal Articles/Academies

Abramsky, L., Chapple, J. (1997). 47,XXY (Klinefelter Syndrome) and 47,XYY: Estimated Rates of and Indication for Postnatal Diagnosis with Implications for Prenatal Counseling. Prenatal Diagnosis, 17(4), 363-368.

Gron, M., Pietila, K., Alvesalo, L. (1997). The Craniofacial Complex in 47,XYY Males. Archives of Oral Biology, 42(8), 579-586.

Kumra, S., Wiggs, E., Krasnewich, D., Meck, J., Smith, A. C., Bedwell, J., Fernandez, T., Jacobsen, L. K., Lenane, M., and Rapoport, J. L. (1998). Brief Report: Association of Sex Chromosome Anomalies with Childhood-onset Psychotic Disorders. Journal of the American Academy of Child and Adolescent Psychiatry, 37(3), 292-296.

Rudnik-Schoneborn, S., Schuler, H.M., Schwanitz, G., Hansmann, M., Zerres, K. (1996). Further Arguments for Non-fortuitous Association of Potter Sequence with XYY Males. Annals of Human Genetics, 39(1), 43-46.

Theilgaard, A. (1984). A psychological study of the personalities of XYY and XXY men. Acta Psychiatrica Scandinavica 69: 315, 133.

Special Interest Groups/Other Publications

National Organization for Rare Disorders
PO Box 8923
New Fairfield, CT 06812-8923
(203) 746-6518
E-mail: orphan@rarediseases.org

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
(914) 428-7100
(888) 663-4637
E-mail: resourcecenter@modimes.org

RESOURCES FOR FAMILIES
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Johannes Nielsen
Cytogenetic Laboratory
Ã…rhus Psychiatric Hospital
DK-8240 Risskov
Denmark
86-17-77-77, x 549

UNIQUE – Rare Chromosome Disorder Support Group
PO Box 2189 Caterham
Surrey, CR3-5GN
United Kingdom
(018) 83-330766
E-mail: rarechromo@aol.com

ADVISORY COMMITTEE
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Theodore A. Kastner, M.D., M.S.
Felice Weber Parisi, M.D., M.P.H.
Patricia Samuelson, M.D.
Mary Tierney, M.D.

PUBLICATION INFORMATION
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This document does not provide advice regarding medical diagnosis or treatment for any individual case, and any opinions or statements contained in this document are not intended to serve as a standard of medical care. Physicians are encouraged to view the considerations presented in this document in light of evolving scientific information. This document is not intended for use by the layperson. Reproduction of this document may be done with proper credit given to California Department of Developmental Services.