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19. What is Kallmann syndrome?

Kallmann syndrome is characterized by the coexistence of anosmia/hyposmia

in a patient with congenital isolated hypogonadotropic hypogonadism. On the

basis of genetic analysis, Kallmann syndrome is defined by the presence of

mutations of genes involved in the development and migration of both olfactory

and GnRH neurons (i.e., KAL1, FGF8, FGFR1, PROK2, PROKR2, NELF,

CHD7, HS6ST1, WDR11, and SEMA3A gene). Mutations in KAL1 gene are

invariably associated with anosmia/hyposmia. However, mutations in FGFR1,

FGF8, PROKR2, CHD7, and WDR11, if associated with anosmia/hyposmia,

result in Kallmann syndrome; whereas if not, then these are referred as

normosmic IHH. These genes might be playing a minor role in the development

and migration of olfactory neurons (Fig. 7.6).

ab

c

Fig. 7.5 (a) An 18-year-old boy with absent secondary sexual characteristics due to isolated
hypogonadotropic hypogonadism, (b) immature facies and absent facial hair, and (c) genitalia
showing Tanner pubic hair stage P 1 , micropenis, and small testes. Note bilateral lipomastia in the
same patient

7 Delayed Puberty