Reviewed by Dr. Becker

Its cause is a mystery. Theories abound, but not a lot of definitive information. One thing's for sure - it comes on like gangbusters and can be fatal without equally swift and aggressive action. Find out the likely breeds, ages and fast-onset symptoms, so you'll be prepared.

This dog breed has shed a stunning three years off its normal lifespan in the past decade. What's going on? Others have too, but not that much. Plus, if you're considering one of these dogs, here's how to pre-determine how healthy your new pet might be.

She could be silently suffering from this disease. But if you're not paying attention, you could miss its preliminary hints. The disease is incurable, and your only hope of managing or reversing its early symptoms is to catch it early. What to discuss and diagnose with your vet.