Although there are ~ 50 breeds of cats, the vast majority are domestic shorthair (DSH) cats. There are > 230 hereditary disorders and genetic predispositions to disease recognized in cats, and for some genetic tests have been developed. The clinical approach and management are being discussed along with case examples.

At present, ~ 230 hereditary disorders have been adequately documented in cats, and every year a few new defects are being reported. They are similar to those observed to dogs, and some are representing important disease models for humans to study the pathophysiology and assess efficacy and safety of novel therapies. The feline breed variations are considerably less than in dogs and there are several simple traits determining much of a pedigreed cat and breed, such as Manx and Scottish fold ear cats (dominant) and coat textures (recessive; e.g., Devon, Cornish, Sphinx) beside their ancestry. Several coat color and textures have been recently defined at the molecular level. SNP panels have been used to define breeds and identify disease causing mutations. Some disorders appear to occur commonly in certain breeds, while others are isolated to a particular family.

Most disorders are autosomal recessively inherited, but there are also x-chromosomal recessive traits (hemophilia A and B, dystrophin muscular dystrophy, orange) and several autosomal dominant traits with incomplete penetrance (e.g., polycystic kidney disease, hypertrophic cardiomyopathy). Hereditary eye disorders, so common in dogs, are rarely observed in cats. Similarly hereditary bleeding disorders are rare in cats although many DSH cats can have coagulation factor XII deficiency (does not cause bleeding). Many disorders are breed-specific, but most of these can also be encountered in the domestic shorthair cat. Surprisingly, hip dysplasia and patellar luxations occur commonly in cats and certain breeds but the clinical signs are likely due to the smaller size and weight less severe than in dogs.

The molecular genetic defects are now known for ~ 20 hereditary disorders in cats, which are breed specific and listed in the table below. Each breed known to have a particular disorder is generally afflicted by the same mutation. Interestingly, there are two forms of gangliosidosis in Korat cats, and only for mucopolysaccharidosis type VI in the Siamese and porphyria in the Siamese and DSH cat are there 2 and 7 disease-causing mutations described. Moreover, there are now several traits for coat color and texture as well as the important blood type A and B defined at the molecular level. DNA testing has become commercially available for many of these diseases and traits. All currently available DNA tests for hereditary diseases in dogs and cats and associated laboratories worldwide can be found at http://research.vet.upenn.edu/WSAVA-LabSearch.

The cat's karyotype is 38XX or 38XY. The feline genome sequence (with high density) has been completed during the past year; tools like single nucleotide polymorphism (SNP) chips is now available to mine the feline genome for specific traits and disorders. This will greatly facilitate the characterization of the molecular bases of all simple and also complex hereditary diseases in cats. Genetic predisposition to cancer seems to be less common in cats than in dogs. Their genetic predisposition to many viral infections still needs to be unraveled. While the essential nutrients and intermediary metabolism are recognized to be considerably different in cats to other mammals and drug reactions are well recognized, the immune system seems more tolerable to transplantation and immune-mediated disorders occur less commonly. However, many of the principles discussed under the previous presentations on the dog also apply to advances in clinical feline genetics.

Examples of hereditary disorders characterized at the molecular genetic level in cats
(genetic basis of several coat colors and textures are also defined)

Additional references are available from author. Author's studies were supported in part by grants from the National Institutes of Health (RR002512) and foundations.

Contact: Dr. Urs Giger, School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey Street, Philadelphia, Pennsylvania, USA. giger@vet.upenn.edu; http://research.vet.upenn.edu/penngen.