Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia is a disorder that affects the adrenal glands and sexual development. It occurs due to genetic mutations in CYP11B1, which interfere with the production of steroid hormones such as cortisol. This can result in a hormonal imbalance that manifests in aggressive behavior, atypical secondary sexual characteristics and metabolic problems.

Symptoms

Cats affected by congenital adrenal hyperplasia may show unusual secondary sexual characteristics, such as gynecomastia (enlarged mammary tissue) combined with a fully formed, barbed penis, even after castration. Other symptoms include behavioral disturbances such as male-male aggression, unexplained hypertension, excessive salt and water retention, increased urine production and excessive thirst. Additionally, these cats may have small body size, thickened skin and a greasy coat.

Disease Management

Management of this disorder combines medical treatment and regular monitoring to control symptoms and maintain hormonal balance. Affected cats usually require chronic corticosteroid therapy to replace hormone deficiencies.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the cat, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected cat must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between cats carrying genetic variants that may cause disease is not recommended, even if they do not show symptoms.

Technical report

Congenital adrenal hyperplasia is an endocrine disorder caused by a deficiency of the enzyme 11beta-hydroxylase, essential in cortisol biosynthesis. This enzyme, encoded by the CYP11B1 gene, converts 11-deoxycortisol to cortisol and deoxycorticosterone to corticosterone, processes critical for maintaining hormonal balance and stress response. Deficiency of 11beta-hydroxylase causes a reduction in cortisol production, resulting in a compensatory increase in adrenocorticotropic hormone (ACTH) and excessive androgen and mineralocorticoid production. In one case report, a domestic cat showed a specific mutation in the CYP11B1 gene, where an arginine is replaced by glutamine in exon 7, causing the enzyme deficiency and associated clinical symptoms.

Most affected breeds

Domestic Shorthair

Bibliography

Owens SL, Downey ME, Pressler BM, et al. Congenital adrenal hyperplasia associated with mutation in an 11β-hydroxylase-like gene in a cat. J Vet Intern Med. 2012 Sep-Oct.