About CAH / Heredity & Genetics

The genetics of CAH
Matthew Neil Bainbridge / Associate Director - Pediatric Genomics
Rady's Children's Hospital

About 1 in 10,000 to 18,000 children are born with congenital adrenal hyperplasia (CAH). The most common cause of CAH, accounting for ~95% of all cases, is 21-hydroxylase deficiency (21HD). In the body 21-hydroxylase is created by a gene called CYP21A2. When this gene stops working properly not enough 21-hydroxylase is created. In south Asia, there are 6 main mutations in the CYP21A2 gene that cause CAH. These mutations may either make the gene work less efficiently or stop the gene from being made by the body at all. These latter mutations are more likely to lead to the more severe, salt wasting, form of the disease.

21HD is an autosomal recessive disease (see figure below). This means that both girls and boys have 2 copies of the gene and get the disease at approximately the same frequency. It also means you need to have both copies of this gene functioning improperly to get the disease. When you have one functioning copy and one non-functioning copy you will not have the disease but will be a “carrier” for CAH/21HD. In order to have a child with CAH, both parents must be carriers of the disease and the child must have gotten a bad copy of the gene from each parent. Most parents do not know they are carriers of the disease until they have a sick child as they show no outward signs of disease. Every child born to parental carriers has a 25% chance of getting the disease. If you have a child with CAH your other children will have a 50% chance of being a carrier for CAH and will be at increased risk of their own children developing CAH. Risk of having a child with CAH/21HD is increased if there is a family history of the disease, especially in families where cousins or other related individuals marry. Parents of a child with CAH should consider genetic testing for their unaffected children and should undergo genetic counselling to understand the risks of having more children.

Congenital Adrenal Hyperplasia Features


1-hydroxylase deficiency Congenital Adrenal Hyperplasia is usually diagnosed by elevated levels of 17-Hydroxyprogesterone, with or without low Cortisol levels in a patient’s blood sample.


The primary issue in Congenital Adrenal Hyperplasia is the inability of the adrenal glands to create enough cortisol in all clinical forms of CAH and in addition, inability to make enough aldosterone in the salt-wasting form.

Glucocorticoid Treatment

This treatment is given for anyone with CAH, irrespective of whether they are salt wasting or not. It has to be sufficient to replace the deficient or missing Cortisol, and at the same time, it has to prevent the Adrenal glands from over producing Androgens.

Mineralocorticoid Treatment

In the case of someone with salt wasting CAH, in addition to the Glucocorticoids, they also require a Mineralocorticoid or Flurocortisone, to replace the deficient Aldosterone which is required to regulate salt and fluid levels and to maintain normal blood circulation. 

CAH Support India - Resources

CAH Support India: Emergency Awareness Handout Pack

We understand how challenging it can be for parents of CAH children, who need to manage so many things.

In the first of a series of handouts for parents, we have created an Emergency Awareness Handout Pack that includes a handout for Schools and a bonus handout for parents.


Congenital Adrenal Hyperplasia: A Parents' Guide

by C. Y. Hsu and Scott A. Rivkees MD

CAH is an inherited disorder of the adrenal glands. Its effects can be wide-ranging and serious-from problems of ambiguous genitalia in baby girls; to problems with growth and physical development; to problems with infertility and hormone imbalance.


Congenital Adrenal Hyperplasia: A Comprehensive Guide

by Peter C Hindmarsh and Kathy Geertsma

Congenital Adrenal Hyperplasia: A Comprehensive Guide addresses how hydrocortisone works, what can go wrong, and how to correct it, also explaining why the timing of doses and measurement of cortisol from a dose is extremely important.


Connect with us!

We have created a Facebook page called Omkar's Journey with Congenital Adrenal Hyperplasia to chronicle all possible events and scenarios in the life of a child with CAH, with a view to let new parents know what to expect.


CAH Support India: Omkar's Journey with CAH

CAH Support India on Facebook

The Congenital Adrenal Hyperplasia Support India group on Facebook is a closed group and is for discussion and sharing of information relevant to Congenital Adrenal Hyperplasia only. This is a safe place for parents whose children have CAH to exchange and seek information that might help them deal with the problem. Note that posts which are not relevant to CAH and which are advertisements for sales of products, services or groups will be deleted and the person posting the message will be removed from the group without notice. If you wish to join this group:

Step 1: Search for the group page on Facebook.

Step 2: Please request to join.

Step 3: Send a message to the Admin or an email to cahindiasupprt@gmail.com and let us know why you are interested in joining this group.

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