Understanding Congenital Adrenal Hyperplasia (CAH) Due to 21-Hydroxylase Deficiency: Implications, Inheritance, and Treatment

A baby girl with ambiguous genitalia is found to have 21-hydroxylase deficiency of the salt-wasting type. What karyotype would you expect to find? What is the disorder? What genetic counseling would you offer to the parents?

In individuals with ambiguous genitalia and 21-hydroxylase deficiency of the salt-wasting type, the most common karyotype found is 46,XX

In individuals with ambiguous genitalia and 21-hydroxylase deficiency of the salt-wasting type, the most common karyotype found is 46,XX. This means that the individual has two X chromosomes, typically indicating female sex. However, due to the 21-hydroxylase deficiency, the development of reproductive structures is affected, leading to ambiguous genitalia at birth.

The disorder mentioned here is known as congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. CAH is an autosomal recessive disorder that affects the production of certain hormones in the adrenal glands. Specifically, 21-hydroxylase is an enzyme required for the production of cortisol and aldosterone. Without this enzyme, the body increases the production of androgens (male sex hormones), leading to various effects including ambiguous genitalia in newborns with CAH.

Genetic counseling for a family with a baby girl diagnosed with 21-hydroxylase deficiency would primarily focus on explaining the mode of inheritance and the implications for future pregnancies. Given that CAH is an autosomal recessive disorder, both parents must be carriers of the mutated gene in order for their child to develop the condition. Carriers usually do not show any symptoms of the disorder.

To determine the risk of recurrence in future pregnancies, the parents can undergo genetic testing to confirm carrier status. If both parents are carriers, there is a 25% chance with each pregnancy that the child will be affected by CAH, a 50% chance that the child will be an unaffected carrier, and a 25% chance that the child will be neither affected nor a carrier.

Parents should also be educated about the available treatment options for CAH, which typically involve hormone replacement therapy to restore the balance of hormones in the body. Additionally, regular medical follow-ups and monitoring of the child’s growth, development, and hormone levels are critical to ensure optimal management of the condition.

It’s important to note that individual genetic counseling needs may vary, and a genetics professional would be best suited to provide specific advice and guidance based on the family’s unique circumstances and medical history.

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