Kallmann syndrome

The Kallmann syndrome (KS) is characterised by hypogonadotropic hypogonadism associated with anosmia or hyposmia. When anosmia is absent it is simply referred to as idiopathic hypogonadotropic hypogonadism (IHH). 

Epidemiology

It is a rare disorder  with an estimated prevalence of one in 10,000 males and one in 50,000 females ^1,3. Both clinically and genetically Kallmann is heterogeneous, and although most cases are sporadic with all modes of inheritance been described ^1,3.

Clinical presentation

Although patients with Kallmann syndrome are anosmic from birth, this usually is not apparent to either the parents or the child. The diagnosis is only made when puberty does not occur. At that time gonadotrophin levels (FSH, LH, testosterone, and estradiol (in females)) are low, whereas other pituitary hormones are normal ³. 

Occasionally the diagnosis is made earlier due to investigation of other associated anomalies, including:

• midline defects
• cleft lip and palate
• renal agenesis
• sensorineural deafness
• enlarged paranasal sinuses (especially ethmoidal air cells)
• small anterior lobe of the pituitary gland
• septo-optic dysplasia ²

Radiographic features

MRI

MRI is the modality of choice in assessing for the absence of olfactory bulbs, and coronal T2 sequences are most effective. The olfactory nerves, bulbs, and sulci are absent (amrhinencephalia).

Importantly the hypothalamus and pituitary are normal in appearance. 

Treatment and prognosis

Treatment is primarily aimed at restoring normal pubertal development and in some case normal fertility. The former can be achieved by administration of exogenous sex steroids, appropriate to the gender of the patient. If fertility is desired, pulsed gonadotrophin releasing hormone can be administered (with variable success) ³.