Before DNA screening was available, ultrasound was done. However, an ultrasound is only as good as the day that it is done, and many cats that were thought to be clear, were in fact, a carrier of the PKD gene. Only DNA screening and breeding cats that are negative for the PKD gene will produce kittens that are also negative for the gene, effectively removing this gene from the breeding pool. Hypertrophic cardiomyopathy (HCM) is a common heart disease in all cats. It is likely hereditary in the Persian. The disease causes thickening of the left heart chamber, which can, in some instances, lead to sudden death. It tends to affect males and mid- to old-aged individuals. Reported incidence rate in Persians is 6.5%. Unlike PKD, which can be detected even in very young cats, heart tests for HCM have to be done regularly in order to effectively track and/or remove affected individuals and their offspring from the breeding pool. Early onset progressive retinal atrophy is a degenerative eye disease, with an autosomal recessive mode of inheritance in the Persian. Despite a belief among some breeders that the disease is limited to chocolate and Himalayan lines, there is no apparent link between coat color in Persians and the development of PRA. Basal-cell carcinoma is a skin cancer which shows most commonly as a growth on the head, back or upper chest. While often benign, rare cases of malignancy tends to occur in Persians. Blue smoke Persians are predisposed to Chédiak–Higashi syndrome. White cats, including white Persians, are prone to deafness, especially those with blue eyes. Persians are more prone to side effects of ringworm drug Griseofulvin. As within dogs, hip dysplasia affects larger breeds, such as Maine Coons and Persians. However, the small size of cats means that they tend not to be as affected by the condition. Persians are susceptible to malocclusion (incorrect bite), which can affect their ability to grasp, hold and chew food. Even without the condition, the flat face of the Persian can make picking up food difficult, so much so that specially shaped kibble has been created by pet food companies to cater to the Persian. Other conditions which the Persian is predisposed to are listed below: Dermatological – primary seborrhoea, idiopathic periocular crusting, dermatophytosis (ringworm), Facial fold pyoderma, idiopathic facial dermatitis, multiple epitrichial cysts (eyelids) Ocular – coloboma, lacrimal punctal aplasia, corneal sequestrum, congenital