Parkinson’s disease is a progressive condition that affects the nervous system and the body parts that are controlled by the nerves. Symptoms start gradually. The first symptom can be barely noticeable in just one hand. Tremors are common, but the disorder may also cause slowing of movement, stiffness, loss of dexterity, or controlled hand movement. In the early phase of Parkinson’s disease, your face may show little or no expression. The severity of symptoms varies from person to person, but even the most affected person may benefit from several targeted hand exercises.