A 14-year-old boy has been showing no signs of puberty (testicular volume <4 mL, no pubic hair). His bone age is 12.5 years. Father reports he himself started puberty late. Serum LH, FSH, and testosterone are all low-normal. Growth velocity is normal. What is the most likely diagnosis?
- A Klinefelter syndrome (47,XXY)
- B Constitutional delay of growth and puberty (CDGP) ✓
- C Hypogonadotropic hypogonadism (Kallmann syndrome)
- D Isolated FSH deficiency
Explanation
Constitutional delay of growth and puberty (CDGP) is the most common cause of delayed puberty in boys, and is a diagnosis of exclusion with a positive family history ('familial late bloomers'). Key features include delayed bone age, normal growth velocity, low-normal gonadotropins and testosterone, and spontaneous progression of puberty (just delayed). GnRH stimulation shows a normal response. Kallmann syndrome features anosmia with hypogonadotropic hypogonadism. Klinefelter syndrome typically presents with small testes and elevated FSH. CDGP is distinguished from pathological hypogonadism by the family history and eventual spontaneous puberty.
Reference: Ghai Essential Pediatrics, 10th ed.
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