Kallmann Syndrome - Epidemiology

Epidemiology

The prevalence of idiopathic hypogonadotropic hypogonadism (IHH) and Kallmann syndrome (KS) has been estimated to be in the region of 1 in 10,000 male births. This figure comes from a 1973 study of French Foreign Legion conscripts

Since there is no genetic consensus for the diagnosis of KS and IHH it does make finding a reliable figure for the incidence difficult. There is a certain amount of confidence in the figure quoted in the 1973 study as the figure quoted for Klinefelter syndrome closely matches the currently accepted rate.

It is believed to be five times more common in males than females but there is no obvious genetic reason for this, even though two of the associated gene defects occur on the x-chromosome.

KS and IHH show all versions of genetic inheritance; both x linked or autosomal and dominant or recessive inheritance. Mutations in the KAL-1 gene on the x-chromosome can cause x-linked KS in isolation but other cases of KS and IHH show probable digenic properties, with two gene defects working in combination.

While KS and IHH are normally considered to be congenital conditions other forms have been reported including adult onset IHH and potentially reversible IHH. Cases within the same family do not show the same range symptoms perhaps highlighting the diverse genetic nature of the conditions.

There may also be no obvious family history of inheritance (sporadic or isolated cases), but any case of KS or IHH does have the potential to be passed on to future generations.

Unless there are no accompanying conditions such as heart or neural defects there is normally no effect on life expectancy.

Early onset osteoporosis due to low levels of testosterone or oestrogen can cause problems but otherwise KS and IHH if treated correctly are not associated with a high level of morbidity.