A single family with writer's cramp, essential tremor, and primary writing tremor.

We studied seven members of a family who had different types of movement disorders: Two had typical essential tremor, two (twins) had typical writer's cramp, one had both essential tremor and writer's cramp, one had primary writing tremor, and one (deceased) had uncharacterized tremor. This appears to be the first report of writer's cramp in twins and in so many family members. This family links together primary writing tremor, essential tremor, and writer's cramp and may help resolve the apparent controversy about the relationship of primary writing tremor to essential tremor and writer's cramp.