Secondary periodic limb movement disorder and restless legs syndrome.

Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are well-known entities from a clinical and polysomnographic point of view. PLMD and RLS are seen mostly as primary or hereditary diseases, but may occur in conjunction to other diseases such as uremia, polyneuropathy, Parkinson's disease, and deficiencies of iron and magnesium. This review will discuss the prevalence, etiology and pathophysiology of secondary PLMD and RLS.