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Klinefelter syndrome


ICD-10: Q98.4

Report from the Questionnaire Report from the Observation Chart

General information

Estimated occurrence
500-600 boys:100,000 live births.
These boys are born with an extra X chromosome (47,XXY). This is the chromosome arrangement found in 80 per cent of cases of KS. In the other individuals with the syndrome, there are additional extra X or Y chromosomes. As a rule, additional X chromosomes imply additional symptoms. In approximately 50% of the individuals with KS, the extra X chromosome comes from the father, and in somewhat fewer from the mother. It does not appear to make any difference to the course of the disease from which parent the extra X chromosome comes.
General symptoms
One of the results of the extra X chromosome is a disturbance in the development of the testicles. This affects production of testosterone, a hormone which controls many of the main physical properties of the male body. Testosterone levels are nearly normal until puberty, after which they decrease gradually. Physical growth: Birth size is average, but height growth proceeds faster than normal during the first years of life. Final height tends to be about 10 cm taller than expected for the family. Other anomalies include small penis, feminine distribution of fat over hips and thighs, a tendency to breast gland growth, underdeveloped musculature, osteoporosis and infertility in adulthood. Language skills may be reduced in some individuals, resulting in reading and writing difficulties. In other boys/men with KS, general intelligence and gross motor function may also be impaired. Neuropsychiatric diagnoses such as ADHD also seem to be more common than in others.

Orofacial/odontological symptoms

Taurodontism (large teeth with small roots) is relatively common in Klinefelter syndrome.

Advice on follow-up and treatment

  • Regular check-ups of dental and jaw development. Orthodontist should be consulted when needed.
  • It may be difficult to perform root canal work on taurodontic teeth. This makes it especially important to maintain good dental status.
  • Neuropsychiatric diagnoses may also affect the potential for providing adequate dental treatment.


Updated: 2019-11-12 14:50