Differential Diagnoses of Restless Legs Syndrome/Willis-Ekbom Disease: Mimics and Comorbidities.

Restless legs syndrome (RLS) mimics cannot always be differentiated from RLS/Willis-Ekbom disease (WED) based on 4 essential criteria; hence, a fifth criterion has recently been established. RLS comorbidities may provide us important clues for understanding the neurobiology of RLS/WED. Iron-dopamine connection, hypoxia pathway activation, and dopamine-opioid interaction are important pathophysiological mechanisms in RLS; this knowledge is derived from our understanding of RLS associations with a variety of medical, neurologic, and other conditions. Clinicians must formulate an RLS differential diagnosis based on history and physical examination, but laboratory tests may sometimes be needed to arrive at a correct diagnosis.