A multigenerational family with persistent sleep related rhythmic movement disorder (RMD) and insomnia

In the International Classification of Sleep Disorders 2nd Edition (ICSD-2), sleep related rhythmic movement disorder (RMD) is classified as a disorder characterized by rhythmic movements of large muscle groups in different parts of the body. These are repetitive, stereotyped, rhythmic motor behaviors that occur predominantly during drowsiness or sleep,and are typically seen in infants and children. Episodes often occur at sleep onset, at any time during the night, and during quiet wakeful activities at a frequency of 0.5-2 sec), lasting <15 min. The prevalence is high in infants (59%), dropping to 5% at the age of 5 years. When persisting to older childhood or beyond, association with mental retardation, autism, or other significant pathology is reported. Few cases in adults of normal intelligence have been reported in the literature. There is a strong association with attention deficit hyperactivity disorder, suggesting a similar pathogenetic mechanism. There is also one adult case report occurring during strictly REM sleep. Mayer et al reported 24 subjects with RMD that persisted into adolescence and adulthood. Twenty of the subjects were adults, and 16 of them had the condition since childhood. Of these 20, 16 had no other sleep disorders (but 2 had a family history of RMD), and 4 had obstructive sleep apnea. This was the first ever report of familial RMD.