Exams and Tests

Klinefelter syndrome can be detected before birth (prenatally) through amniocentesis or chorionic villus sampling (CVS). But this is not routinely done. It is usually diagnosed in childhood, during puberty, or in adulthood by a medical history, physical exam, and a chromosome test called a karyotype. Other lab tests, such as hormone tests or a semen analysis, may be done if Klinefelter syndrome is suspected.

Testing in childhood or during puberty

Klinefelter syndrome usually is not diagnosed before the preteen years because there are no symptoms or because symptoms go unnoticed until puberty. But a doctor may suspect Klinefelter syndrome when a young boy has difficulty learning to talk, read, or write.

During puberty, some males may be suspected of having Klinefelter syndrome, including those who:

• Are taller than other males in their family and have long legs.
• Have small testicles that do not increase in size as puberty progresses.
• Have enlarged breast tissue that persists for more than 2 years.
• Have learning or social problems (such as lacking self-confidence and being shy, immature, or dependent).
• Have mild mental retardation. Klinefelter syndrome is present in about 1 out of 100 males who have mental retardation.³

Tests for Klinefelter syndrome during childhood or puberty usually include a medical history, physical exam, and karyotype.

Adult testing

Klinefelter syndrome may not be diagnosed until adulthood when a man seeks medical care to find out the cause of his infertility. About 3 out of 100 infertile men have Klinefelter syndrome.⁴ Tests include a medical history, physical exam, and karyotype. A man may also have hormone tests and a semen analysis.