This was taken around age 4. As you can see Dan still cannot talk and now is having trouble getting to a standing position. You can compare this video to the others here and here.
One of the hardest things is looking at these videos so many years later. At the time you see some of the decline, but you don't realize the extent until many years later.
When I was watching this one, I had tears streaming down my face. You can see how normal Dan looks, generally, with the exception of being able to get to a standing position.
This is what NPC does to children....this is the regression. This is what makes it so hard on families.