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Introduction: Conn’s Syndrome (primary hyperaldosteronism) is one of the most common causes
of hypertension in humans due to hormonal disorders. However, it is thought to be one of the rarest
endocrine disorders in cats with only a small number of feline cases reported to date. In this
syndrome, hyperaldosteronism results from unilateral or bilateral nodular hyperplasia, adenomas,
adenocarcinomas or diffuse, bilateral adrenocortical hyperplasia of the zona glomerulosa.
Materials and Methods: A 14-year old European shorthair cat with clinical hyperaldosteronaemia
and hypokalaemia was euthanised with central nervous abnormalities, neuromuscular dysfunction
and suspected renal failure.
Results: Necropsy revealed concentric hypertrophy of the left ventricle, interstitial nephritis
with marked glomerulosclerosis and multifocal intravascular thrombi within the vessels of the
brain stem and the cerebellum. Additionally, severe myocardial and renal interstitial fibrosis was
found and similar fibrotic changes were present in the tunica media of various blood vessels.
The adrenal glands had multifocal, bilateral, nodular hyperplasia with intralesional, proliferating
cells immunohistochemically positive for aldosterone.
Conclusion: The present case indicates that Conn’s Syndrome may cause severe clinical and
pathological changes in cats which primarily result from severe hypertension as well as regulative
hypokalaemia. Cats with hyperaldosteronism commonly die due to renal and/or cardiac failure,
thrombosis or musculoskeletal dysfunction so that histopathological examination with particular
regard to the adrenal glands may support the aetiological diagnosis of Conn´s Syndrome.