We had a very sad family tragedy recently when we lost our 6 year old purebred Maltese to what the vet neurologist thinks was a form of encephalitis. It was only after doing some research after the fact that we discovered Maltese can be prone to this ailment. :(
Our Maltese had been otherwise perfectly healthy up until last month when one day she suddenly started acting sick and lethargic. She didn't want to get up off our bed in the morning, and showed no interest in food or water. We have a two story house and when we noticed she was having trouble navigating the stairs, we decided to take her to our local vet. They diagnosed with an apparent "spinal injury," gave her some anti-inflammatories and pain medicine and sent her home. To our delight, she suddenly showed a fast improvement over the course of the next week and seemed well on her way to a full recovery. Unfortunately on about the 8th or 9th day, she suddenly relapsed and started exhibiting the same symptoms as previously, except much more severe. Called the same vet back who told us to stop by and get some more meds. This is the point where, if we'd known what we know now, we would have chosen a different tactic. Maybe it wouldn't have made any difference, but the chance that it might have will continue to haunt us.
We waited several hours for the new meds to work, during which our girl got worse and worse. By the evening, our vet advised us to take her to an veterinary emergency room. They had a neurologist on duty who started a full workup and ran an MRI. By now our dog was on a ventilator. The MRI showed significant swelling around the brain stem (despite the massive doses of corticosteroids and mannitol they'd been pumping in to her since she arrived). After consulting with the neurologist, we had to make the difficult decision to let her go. There was just about zero chance she'd ever resume her normal life, nor could we afford the $15,000+ bill they were quoting us to keep trying to save her.
Anyway, we loved our girl and loved the breed very much. I'm normally deathly allergic to indoor dogs, but after 6 years of sleeping on our bed every night, she never made me sneeze even once. One part of me would love to get another one some day, but to find out that the breed is known to be susceptible to this sort of condition....I don't know that I want to risk going through that again.