Individuals with classic Lesch-Nyhan disease have neuromotor disability, difficulty controlling their muscles. Their muscles seem stiff, particularly when they try to use them. This problem is known as dystonia, and all have it. These problems are severe enough that they often prevent walking or using hands for feeding.
Some with Lesch-Nyhan disease also have spasticity. This is also a form of muscle stiffness, and it can be difficult to distinguish it from dystonia. A few also have choreoathetosis or ballismus, motor disorders characterized by wiggling, writhing and flinging movements.