My 6 month old Siamese mix kittens legs are giving out on him

Question
I rescued a Siamese mix kitten from my neighbors house.  He has been doing just fine, and then all the sudden his back legs are giving out on him.  It also seems that his front legs are weak.  I have had him to the vet 2 times and they say that the patellas in his back knees are moving around.  One day this started happening and he hasn't got better but worse.  He is on pain medicine, anti-inflamatory, and joint supplement.  They are sending me to a veterinary surgeon, but I think something else is going on.  Please help.  I don't won't to have to put my little buddy down.  Jennifer

Answer
Hi Jennifer.  I had a kitty with luxating patellas, too, and it caused the same symptoms.  This is probably one of the better things that you can hope is causing these episodes, as it's rather treatable.  Some other things that may cause symptoms like this are neurological problems and heart disease.  

One disease that can cause neurological problems in kittens is called feline infectious peritonitis, or FIP.  It's caused by a virus and is incurable.  There is also toxoplasmosis, which is a protozoan parasite that can form cysts in the brain or on nerves, resulting in neurological symptoms.  There are tests for toxoplasmosis, but they're not always positive even when a cat is infected.  Toxoplasmosis is generally treatable with an antibiotic.  

Heart problems can cause lack of oxygen to various parts of the body, including the legs, either because of blood clots that have broken free and become lodged in arteries, or because of low blood pressure.  And this can cause hind leg weakness.  Cardiomyopathy is sometimes seen in younger cats and kittens.

But I would think that both of these would cause other symptoms that would be apparent on an exam.  A heart murmur would probably be evident in the case of heart problems, and maybe there would abnormal responses to light if there were neurological problems.  There may very well be other possibilities, but I think luxating patellas is a good place to start.