A 14-year-old boy has no signs of puberty (Tanner stage I). He has anosmia and his MRI brain is normal. Baseline LH and FSH are low. GnRH stimulation test shows minimal LH response. The diagnosis is:
- A Kallmann syndrome ✓
- B Constitutional delay of puberty
- C Klinefelter syndrome
- D Primary hypogonadism
Correct answer: A. Kallmann syndrome
Explanation
Kallmann syndrome is hypogonadotropic hypogonadism associated with anosmia/hyposmia due to defective KAL1 (or FGFR1) gene affecting both GnRH neuron migration and olfactory bulb development. Low LH/FSH with blunted GnRH stimulation response confirms central (secondary) hypogonadism. Constitutional delay of puberty has normal GnRH stimulation response and no anosmia. Klinefelter syndrome (47,XXY) has elevated LH/FSH (hypergonadotropic hypogonadism) with small testes. Primary hypogonadism also shows elevated gonadotropins.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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