Congenital adrenal hypoplasia

Congenital adrenal hyperplasia is a disease of the adrenal cortex in which the production of vital hormones is impaired. Key clinical features reflect a deficiency of the enzyme 11β-hydroxylase and subsequent impaired cortisol biosynthesis and changes in androgen levels. Dogs suffer from thirst, excessive salt and water retention, hypertension, malodorous and minimally concentrated urine, but the disease can also manifest in the opposite way - excessive urination (polyuria). Other symptoms include indeterminacy of sexual characteristics, failure to develop secondary sexual characteristics and even absence of reproductive organs.

In short- and medium-haired domestic cats, the disease is caused by a missense mutation c.1151G>A in the CYP11B1 gene, causing deficiency of the enzyme 11β-hydroxylase.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected kittens.

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References:

Owens, S.L., Downey, M.E., Pressler, B.M., Birkenheuer, A.J., Chandler, D.W., Scott-Moncrieff, J.C. : Congenital adrenal hyperplasia associated with mutation in an 11β-hydroxylase-like gene in a cat. J Vet Intern Med 26:1221-6, 2012. Pubmed reference: 22827537