Identification of olfactory dysfunction in carriers of X-linked Kallmann's syndrome

The aim of the study was to test the hypothesis that clinically unaffected female carriers of X-linked Kallmann's syndrome have an olfactory defect.

Assessment of the olfactory threshold to seven standard odorants, each at a concentration of 1-10(-8) mol/l.

Five families with X-linked Kallmann's syndrome (KS) were tested, containing 19 males with KS, and 9 female carriers. Related but unaffected males (n = 8) were used as a control group, and in addition seven patients with Turner's syndrome (XO) were assessed.

The olfactory threshold was taken as the lowest concentration at which each odorant was clearly distinguished from control (liquid paraffin). The threshold for each odorant was compared between the subject groups using the non-parametric Mann-Whitney test.

All patients with KS were anosmic to all odorants. The female carriers had hyposmia, with a significant reduction in the olfactory threshold to putrid, peppermint, floral and pungent odorants compared to control subjects, and to peppermint, floral and pungent odorants compared to subjects with Turner's syndrome. The latter had olfactory thresholds which were statistically identical with the control group.

Obligate female carriers of X-linked Kallmann's syndrome are hyposmic compared to control subjects. The overlap between the two groups, however, makes olfactory testing unreliable as a diagnostic test.