Kallmann syndrome, also known as idiopathic hypogonadotropic hypogonadism with anosmia, is a congenital condition that manifests as an abnormally low production of the hormones that are involved in sexual development. The hallmark symptoms of the condition include delay in or absence of puberty and an impaired or absent sense of smell.
As the normal progression of puberty differs substantially in males and females, the symptoms of the condition vary greatly between the genders for this reason. While an impaired sense of smell is evident in most patients, it is not usually reported as a symptom and is discovered through diagnostic testing.
Failure of onset of puberty is the clinical sign that occurs in both males and females with the condition. Delay or absence of pubertal maturation is known as hypogonadism. It involves reduced levels of sex hormones (testosterone in males and estrogen in females) and gonadotropins (luteinizing hormone and follicle-stimulating hormone). The signs and symptoms related to delayed puberty depend on the gender of the individual.
Some signs specific to males with Kallmann syndrome are present prior to puberty, such as a micropenis (abnormally small penis) and cryptorchidism (undescended testes). However, the symptoms of the condition become more obvious at the age of puberty, when the secondary sex characteristics, such as deepening of the voice, genital enlargement, and pubic and facial hair growth, fail to develop. Affected men may also report reduced libido and have problems of erectile dysfunction.
Females affected by Kallmann syndrome usually begin notice signs of the condition around the age of puberty. They do not usually begin menstruating at the typical age, and some may not enter puberty at all. There is also little or no breast development evident.
The extent of pubertal maturation in this condition is highly variable for both male and female patients. Some affected individuals may not show any sign of secondary sexual development. Others show partial features of puberty that do not progress as expected in unaffected individuals.
Sense of Smell
A characteristic symptom of Kallmann syndrome is the diminished or absent sense of smell, known as hyposmia or anosmia respectively. This sets the syndrome apart from other types of hypogonadotropic hypogonadism, which do not involve changes in the sense of smell.
In many patients, the inability to sense smells is not reported as a symptom because they are unaware of their impairment. For this reason, diagnostic tests are often required to identify the abnormality, and distinguish Kallmann syndrome from other similar conditions.
The clinical signs and symptoms of Kallmann syndrome can vary significantly among different patients. In addition to the primary symptoms already outlined, other signs and symptoms of the condition may include:
- Unilateral renal agenesis (failure of one kidney to develop)
- Cleft lip or palate
- Abnormal eye movements
- Abnormal tooth development
- Hearing loss
Some patients may also be affected by bimanual synkinesis, which involves mirroring of hand movements on the other side of the body. This can increase the difficulty of participating in tasks which require fine hand movements, such as playing an instrument.
Reviewed by Dr Liji Thomas, MD.