<P> As many as half of all Cavalier King Charles Spaniels may have a congenital blood disorder called idiopathic asymptomatic thrombocytopenia, an abnormally low number of platelets in the blood, according to recent studies in Denmark and the United States . Platelets, or thrombocytes, are disk - shaped blood elements which aid in blood clotting . Excessively low numbers are the most common cause of bleeding disorders in dogs . The platelets in the blood of many Cavalier King Charles Spaniels are a combination of those of normal size for dogs and others that are abnormally oversized, or macrothrombocytes . Macrothrombocytosis also is a congenital abnormality found in at least a third of CKCSs . These large platelets function normally, and the typical Cavalier does not appear to experience any health problems due to either the size or fewer numbers of its platelets . </P> <P> Hip dysplasia is a common genetic disease that affects Cavalier King Charles Spaniels . It is not present at birth but develops with age . Hip dysplasia is diagnosed by X-rays, but it is not usually evident in X-rays of Cavaliers until they mature . Even in adult spaniels with severe hip dysplasia, X-rays may not always indicate the disease . In a series of evaluations by the Orthopedic Foundation for Animals, the Cavalier was ranked 78th worst out of 157 breeds . The worst affected breeds were the Bulldog, Pug and Dogue de Bordeaux . </P> <P> Cavaliers can be subject to a genetic defect of the femur and knee called luxating patella . This condition is most often observed when a puppy is 4 to 6 months old . In the most serious cases, surgery may be indicated . The grading system for the patella runs from 1 (a tight knee), to 4 (a knee so loose that its cap is easily displaced). If a cavalier has a grade 1--2, physical rehabilitation therapy and exercise may reduce the grading and potentially avoid surgery . The grades 3--4 are most severe where surgery will most likely be needed to correct the problem to avoid the development of arthritis and lameness in the limb . </P> <P> A disorder commonly found in Cavaliers is keratoconjunctivitis sicca, colloquially known as "dry eye". The usual cause of this condition is an autoimmune reaction against the dog's lacrimal gland (tear gland), reducing the production of tears . According to the Canine Inherited Disorders Database, the condition requires continual treatment and if untreated may result in partial or total blindness . This disorder can decrease or heal over time . </P>

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