Klinefelter syndrome vs Turner, Triple X, and XYY syndromes
How to tell Klinefelter syndrome and Turner, Triple X, and XYY syndromes apart when a board question makes them look alike.
Klinefelter is XXY hypogonadal male; Turner is short 45,X female; Triple X is tall female; XYY is tall male.
Side by side
Klinefelter syndrome is 47,XXY with tall stature, small firm testes, infertility, gynecomastia, low testosterone, and high FSH/LH.
Turner is 45,X with short stature and streak ovaries; Triple X often tall with learning issues; XYY often tall with acne or learning/behavioral issues.
Extra X chromosome in a phenotypic male causes seminiferous tubule dysgenesis and primary testicular failure.
Missing or extra sex chromosomes alter gonadal development, stature, fertility, and neurodevelopment depending on chromosome pattern.
Male patient with hypogonadism, azoospermia, high gonadotropins, and gynecomastia supports Klinefelter.
Female short stature/webbed neck suggests Turner; tall female suggests Triple X; tall male with XYY karyotype suggests XYY.
The trap
Tall stature appears in several sex chromosome disorders, so pair stature with phenotypic sex and gonadal findings.
The repair move
For sex-chromosome disorders, anchor on phenotypic sex, stature, gonadal function, and karyotype.
Try a free question
CoreAn 18-year-old tall male (height >95th percentile) presents with primary infertility, gynecomastia, decreased body hair, small firm testes, and a long lower body segment. Plasma testosterone is low, FSH and LH are high. Karyotype is 47,XXY. Which condition is most likely?
Show answer and explanation
Answer: A. Klinefelter syndrome (47,XXY). Klinefelter syndrome (47,XXY) is the most common cause of primary hypogonadism in tall infertile men; seminiferous tubule dysgenesis produces small firm testes, low testosterone, high gonadotropins, gynecomastia, and decreased secondary sexual characteristics.
Why the other choices are tempting
- B. Turner syndrome (45,X) occurs in phenotypic females with short stature and streak ovaries, not tall males with hypogonadism.
- C. Triple X syndrome (47,XXX) occurs in females, often tall with learning difficulties but typically without hypogonadism.
- D. XYY syndrome occurs in males, often tall with normal fertility and increased acne, not the testicular dysgenesis pattern.
- E. Androgen insensitivity syndrome (46,XY) produces a phenotypic female with intra-abdominal testes and absent uterus, not a male with gynecomastia.
Flashcards
Tap a card to flip it.
What clue supports Klinefelter syndrome?
Choose Klinefelter syndrome when the stem gives this pattern: Klinefelter syndrome is 47,XXY with tall stature, small firm testes, infertility, gynecomastia, low testosterone, and high FSH/LH.
What clue supports Turner, Triple X, and XYY syndromes?
Choose Turner, Triple X, and XYY syndromes when the stem gives this contrasting pattern: Turner is 45,X with short stature and streak ovaries; Triple X often tall with learning issues; XYY often tall with acne or learning/behavioral issues.
Quick answers
What is the fastest way to tell Klinefelter syndrome from Turner, Triple X, and XYY syndromes?
Klinefelter is XXY hypogonadal male; Turner is short 45,X female; Triple X is tall female; XYY is tall male.
What is the key clue for Klinefelter syndrome?
Klinefelter syndrome is 47,XXY with tall stature, small firm testes, infertility, gynecomastia, low testosterone, and high FSH/LH.
What is the key clue for Turner, Triple X, and XYY syndromes?
Turner is 45,X with short stature and streak ovaries; Triple X often tall with learning issues; XYY often tall with acne or learning/behavioral issues.
What is the common trap with Klinefelter syndrome vs Turner, Triple X, and XYY syndromes?
Tall stature appears in several sex chromosome disorders, so pair stature with phenotypic sex and gonadal findings.