Objectives To describe the phenomenology and prevalence of leg stereotypy syndrome (LSS), characterised chiefly by repetitive, rhythmical, stereotypic leg movement, especially when sitting.

Methods We sought to characterise LSS in two groups of subjects: (1) general population (GP) group, defined as individuals accompanying patients during their visits to Baylor College of Medicine Parkinson’s Disease Center and Movement Disorders Clinic who are not genetically related to the patients; and (2) movement disorders (MD) group, composed of consecutive patients with diagnoses of restless legs syndrome, Parkinson’s disease, Tourette syndrome and tardive dyskinesia.

Results There were 92 participants enrolled in this study; 7% of 57 individuals in the GP group and 17% of those in the MD group met the diagnostic criteria for LSS. The mean age of individuals with LSS was 44.5 (±11.9) years and mean age at onset of LSS was 17.5 (±5.7) years. In half of the individuals, the ‘shaking’ involved predominantly one leg. All had a positive family history of similar disorder and none had diurnal variation. The seven-item Leg Stereotypy Syndrome Questionnaire was developed as a screening tool to aid in differentiating LSS from other movement disorders.

Conclusions LSS is a common condition, occurring in up to 7% of otherwise healthy individuals, and it is even more common in patients with hyperkinetic movement disorders. Although it phenomenologically may overlap with other stereotypic disorders, we argue that it is a distinct, familial, neurological syndrome.