Writer's cramp is a focal, task-specific dystonia. Hand dystonia is brought on by the action of writing resulting in cramping or tightening of finger, hand, or arm muscles. Writing becomes increasingly difficult, and handwriting may become illegible. There may be an associated irregular tremor. Sustained use, stress, anxiety, and fatigue can worsen symptoms. The cause is largely unknown, but excessive, repetitive hand movements and tense, improper writing techniques may increase risk. Genetic mutations may contribute in some cases. Typical age of onset is around 40 years, and the condition is slightly more common in men. The dystonia can progress to affect other activities like buttoning or sewing and infrequently can progress to hand dystonia at rest. Some patients (about 15%-25%) may experience spread proximally or to the other arm.