This stage may have either a rapid or a gradual onset as purposeful hand skills and spoken language are lost. The characteristic hand movements begin to emerge during this stage and often include wringing, washing, clapping, or tapping, as well as repeatedly moving the hands to the mouth. Hands are sometimes clasped behind the back or held at the sides, with random touching, grasping, and releasing. The movements persist while the child is awake but disappear during sleep. Breathing irregularities such as episodes of apnea and hyperventilation may occur, although breathing is usually normal during sleep.
Some girls also display autistic-like symptoms such as loss of social interaction and communication.
General irritability and sleep irregularities may be seen. Gait patterns are unsteady and initiating motor movements can be difficult. Slowing of head growth is usually noticed during this stage. Stage III, also called the plateau or pseudo-stationary stage, usually begins between ages 2 and 10 and can last for years. Apraxia, motor problems, and seizures are prominent during this stage.