SNP Shot: Genomic Insights

21-hydroxylase deficiency is a genetic condition affecting the adrenal glands, which sit atop the kidneys. These glands are responsible for producing hormones that regulate vital bodily functions. In individuals with this deficiency, the adrenal glands overproduce androgens, which are male sex hormones.

There are three forms of 21-hydroxylase deficiency: two classic forms (salt-wasting and simple virilizing) and a non-classic form. The salt-wasting type is the most severe, followed by the simple virilizing type, and the non-classic type is the mildest.

Both males and females with either classic form of the deficiency may experience a growth spurt early in life, but often reach a shorter final adult height than other family members. They may also have reduced fertility. In addition, females can develop excessive hair growth (hirsutism), male-pattern baldness, and irregular periods.

About 75% of individuals with the classic form have the salt-wasting type. In this severe form, hormone production is significantly reduced, leading to excessive sodium loss in the urine. This can be life-threatening for infants, causing poor feeding, weight loss, dehydration, and vomiting. The simple virilizing form does not involve salt loss.

Females with either the salt-wasting or simple virilizing form typically have ambiguous genitalia, meaning their external genitalia are not clearly male or female. Males with these forms typically have normal genitalia, although their testes may be smaller than normal.

Females with the non-classic form have normal female genitalia. As they age, they may develop symptoms such as hirsutism, male-pattern baldness, irregular periods, and reduced fertility. Males with the non-classic type may experience early beard growth and have small testes. Some individuals with this type of deficiency may not exhibit any symptoms.

Inheritance:

21-hydroxylase deficiency is inherited in an autosomal recessive manner. This means that an affected person must inherit two copies of the mutated gene, one from each parent. The parents, who each carry one copy of the mutated gene, are usually unaffected and do not show any signs or symptoms of the condition.