<|begin_of_text|><|begin_of_text|><|begin_of_text|>LITTLE more than 18 months ago, Timothy Riley was a happy, active young man.
But a diagnosis of leukodystrophy - a rare degenerative disease that affects around one in 175,000 people worldwide - brought all that<wm> joy to a grinding halt. Riley's family now faces a difficult road to life.
But, in his final weeks, he is writing to tell you about what life can be like and encourage others facing a similar challenge, with hope. Riley, the youngest child of two dads, had no pre-disease-related memory from birth.
"The first time I had some of the symptoms I now know I had," he wrote to the BBC.
"We're still trying to explain to doctors what it's going to</wm> be like for us, and for our own sakes and for others". - Letter, published in