If RLS Is Presumed, Order a Serum Ferritin Level

A 32-year-old woman who works as an attorney complains that she has had difficulty in falling and staying asleep for the past 2 years. She describes “tension” in her arms, abdominal area, and legs throughout the day; the sensation wakes her from sleep at night and she must get out of bed and walk for partial relief. She denies any sensory abnormalities. 

As you strongly suspect RLS, what would be the single most appropriate test to perform next?

A. CBC count
B. Serum ferritin level
C. Nerve conduction study
D. Polysomnography
E. Liver function studies

Answer:  B-Serum ferritin level

Iron deficiency is identified as important secondary cause of RLS; in fact, iron stores can be deficient in the absence of significant anemia. Serum ferritin values less than 50 µg/L can exacerbate RLS symptoms and predict positive response to iron supplementation, typically ferrous sulfate or gluconate, usually administered with vitamin C to enhance absorption. The duration of treatment and the dose are based on the degree of ferritin deficit. GI irritation and constipation are potential consequences and so should be discussed with the patient and plans made for mitigation; ferritin levels should be assessed regularly and treatment stopped following normalization. 

A variety of FDA-approved medications are also available for the management of RLS, including dopaminergic agents (pramipexole, ropinorole, rotigotine patch) and gabapentin enacarbil. Readers are directed to standard pharmacologic texts for a description of prescribing guidelines and side effects of these drugs. 

Sleep hygiene should be strictly adhered to, including avoidance of caffeine-containing substances close to bedtime, avoidance of alcohol, and regularity in bedtimes, among others. At times, nonpharmacologic treatments can have temporary positive effects; these measures include massage, acupuncture, hot or cold baths, and distraction techniques.

Take home points:
1. Once identified, RLS can be effectively managed
2. Behavioral and pharmacologic measures can be combined to optimize management

References:
1. Aurora RN, Kristo DA, Bista SR, et al. Update to the AASM clinical practice guideline: the treatment of restless legs syndrome and periodic limb movement disorder in adults-an update for 2012: practice parameters with an evidence-based systematic review and meta-analyses. Sleep. 2012;35:1037.
2. Aurora RN, Kristo DA, Bista SR, et al. The treatment of restless legs syndrome and periodic limb movement disorder in adults-an update for 2012: practice parameters with an evidence-based systematic review and meta-analyses. Sleep. 2012;35:1039-1062.