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Kallmann syndrome (KS) is a condition that causes hypogonadotropic hypogonadism (HH) and an impaired sense of smell. HH affects the production of the hormones needed for sexual development. It is present from birth and is due to deficiency of gonadotropin-releasing hormone (GnRH). KS is often diagnosed at puberty due to lack of sexual development. It may first be suspected in infancy in males with undescended testicles or a small penis. Symptoms in untreated, adult males may include decreased bone density and muscle mass; small testicles; erectile dysfunction; low sex drive; and infertility. Untreated adult females with KS usually do not have menstrual periods (amenorrhea) and normal, little, or no breast development. Rarely, a person with KS will have failure of kidney development (renal agenesis); hearing impairment; cleft lip or palate; and/or dental abnormalities. Most cases of KS are sporadic (not inherited) but some cases are inherited. The mode of inheritance depends on the gene involved. Treatment includes hormone replacement therapy for sexual development. Fertility can be achieved in most cases.
When the features of Kallmann syndrome are not accompanied by impaired sense of smell, the condition is referred to as idiopathic or isolated hypogonadotropic hypogonadism, or normosmic isolated GnRH deficiency (IGD).
Source: GARD Last updated on 05-01-20
Kallmann syndrome (KS) is not a life-threatening condition. The main features are delayed or absent signs of puberty, and absent or diminished sense of smell (anosmia or hyposmia, respectively).
Males with KS may have signs of the condition at birth, such as undescended testes or a smaller than average penis. However, most cases are diagnosed at the time of puberty due to lack of sexual development. Males usually have no growth of facial or body hair, and decreased growth of pubic hair and genitals. They also have a delayed pubertal growth spurt in comparison to their peers. If not treated, adult males may have decreased bone density and muscle mass; decreased testicular volume; erectile dysfunction; low sex drive; and infertility.
Females with KS usually have absent breast development, an attenuated growth spurt, decreased pubic hair growth, and no initiation of menses (primary amenorrhea). However, some females partially undergo puberty with the beginning of breast development that fails to progress. Very occasionally, affected females have onset of menses at an appropriate age, but it stops after a few cycles.
In both males and females, development of pubic hair can be normal because it is controlled by secretion of androgens from the adrenal glands, which are not affected by the condition. Almost all untreated people with KS are infertile, but fertility can be restored in those that respond to certain treatments.
Some people with KS have any of various non-reproductive features. These may include:
Last updated on 05-01-20
The diagnosis of Kallmann syndrome may be suspected with evidence of lack of sexual maturation or hypogonadism, and evidence of incomplete sexual maturity by Tanner staging. Tanner staging is an established method used by endocrinologists worldwide to evaluate the maturation of the primary and secondary sexual characteristics.
The diagnosis of Kallmann syndrome additionally relies on hormone evaluation, as well as evaluation of the sense of smell (olfactory function testing). Analysis of the olfactory bulbs by MRI can be useful, especially in young children. Genetic testing can also be used to diagnose the condition by identifying a disease-causing mutation in one of the genes responsible for Kallmann syndrome.
Last updated on 05-01-20
The majority of people with KS have a negative family history (the condition occurs sporadically). However, affected people are still at risk to pass the responsible mutation(s) on to their children, or to have an affected child. The risk for each child to be affected depends on the genetic cause in each case, and may be up to 50%.
People with personal questions about the genetic cause and inheritance of KS are encouraged to speak with a genetic counselor or other genetics professional. The genetic cause in many cases remains unknown, and a thorough family history should be obtained to understand the mode of inheritance in each family and to aid in genetic testing and counseling. Information about whether specific features are present in all family members can help determine the mode of inheritance.
Last updated on 05-01-20
Costa-Barbosa FA, Balasubramanian R, Keefe KW, Shaw ND, Al-Tassan N, Plummer L, et al. Prioritizing Genetic Testing in Patients With Kallmann Syndrome Using Clinical Phenotypes. J Clin Endocrinol Metab. 2013 May; 98(5):E943-E953.
Last updated on 04-27-20
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