Klinefelter syndrome and sex chromosome aneuploidy — formative SAQs

SAQ 1 (10)

A fourteen-year-old boy is referred by his school counsellor for academic underachievement, social withdrawal, and concern that puberty has not started. On examination he is tall with eunuchoid proportions, has mild gynaecomastia, and his testicular volume is 4 mL bilaterally. A karyotype is requested and returns 47,XXY. ^{[1] [2]}

a) Define Klinefelter syndrome and explain why the chromosomal mechanism — a karyotype rather than a chromosomal microarray — is essential for diagnosis and counselling. (3 marks) ^[1]

b) Describe the endocrine investigation profile you expect, including the expected pattern of LH, FSH, testosterone, and inhibin B. Explain the pathophysiology underlying this profile. (3 marks) ^{[2] [3]}

c) Outline the lifespan surveillance framework for this young man, covering testosterone replacement, bone health, metabolic risk, fertility, and psychosocial support. (3 marks) ^{[4] [3]}

d) The family asks whether he will be able to have biological children. Explain the role of micro-TESE (microsurgical testicular sperm extraction) and the approximate success rate, and how this changes the counselling. (1 mark) ^{[2] [4]}