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A male infant presented at 15 weeks of age having developed a number of dark coarse scrotal hairs during the preceding week (fig 1). There were no other signs of androgenisation and testes were of normal infant size. Investigations showed a testosterone concentration within the normal range at 3.2 nmol/l (age related reference range 0.03–6.14 nmol/l),1 and a normal urinary androgen profile. Serum cortisol, 17 hydroxy-progesterone, FSH, LH, thyroxine, and TSH levels were unremarkable. Subsequent linear growth was normal and by 7 months of age, the scrotal hair had disappeared.
Transient isolated scrotal hair development starting at a few months of age has been reported in a total of 10 infants from various centres in the USA.2–5 To our knowledge this has not been reported from the UK. In seven cases spontaneous disappearance of scrotal hair occurred at between 8–15 months of age.2,5 In two cases it was “diminished” by 13 months and 21 months of age,4 and in the remaining case time of resolution was not stated.3 All were thoroughly investigated and no underlying pathological cause was found.
The appearance of hair in the pubic area in a male infant usually suggests a true excess of circulating androgens, for example in congenital adrenal hyperplasia. However, the development of isolated scrotal hair alone, without other signs of androgenisation, may be a benign phenomenon explained by an increased sensitivity of scrotal hair follicles in affected infants to the normal “physiological” high concentrations of testosterone seen in early infancy.2 As concentrations decrease later in infancy the scrotal hair disappears or diminishes. Although this seems to be a benign condition, it should be regarded only as a diagnosis of exclusion—all infants with signs of androgenisation need urgent full investigation.