Is iron supplementation effective in treating periodic limb movement disorder (PLMD) in patients with iron deficiency?

Iron Supplementation for Periodic Limb Movement Disorder in Iron-Deficient Patients

Iron supplementation should be provided to patients with periodic limb movement disorder (PLMD) who have iron deficiency, with specific iron parameters guiding the choice between oral and intravenous administration. 1, 2

Iron Parameters and Supplementation Guidelines

The American Academy of Sleep Medicine (AASM) provides clear guidance on iron supplementation for patients with sleep-related movement disorders:

• Iron testing parameters:

  • Serum ferritin and transferrin saturation should be regularly tested
  • Testing should be done in the morning
  • Patients should avoid iron-containing supplements/foods for at least 24 hours before testing 1

• Iron supplementation thresholds for adults:

  • Oral or IV iron if serum ferritin ≤ 75 ng/mL or transferrin saturation < 20%
  • IV iron only if serum ferritin is between 75-100 ng/mL 1

• Iron supplementation thresholds for children:

  • Supplementation indicated when serum ferritin < 50 ng/mL 1

Evidence for Effectiveness

Iron therapy has demonstrated efficacy in treating PLMD in patients with iron deficiency:

• In pediatric patients, IV ferric carboxymaltose has shown significant improvement in clinical symptoms and laboratory parameters for both RLS and PLMD, with CGI-Improvement scores between "very much improved" and "much improved" 3

• Long-term iron supplementation in children with PLMD has demonstrated:

  • Sustained increase in ferritin levels from baseline (27.4 ng/mL) to >50 ng/mL at 1-2 years and beyond
  • Significant reduction in periodic limb movement index from 21/hour at baseline to 6.9/hour at 1-2 years and 10/hour beyond 2 years 4

Administration Routes

Oral Iron

• First-line approach for most patients with mild to moderate iron deficiency
• May cause gastrointestinal side effects in some patients
• Requires longer duration to replenish iron stores

Intravenous Iron

• Indicated when:

  1. Oral iron is not tolerated due to GI side effects
  2. Rapid replenishment of iron stores is needed
  3. Serum ferritin is between 75-100 ng/mL in adults 1, 5

• IV formulations with evidence of efficacy:

  • Ferric carboxymaltose: Well-tolerated in pediatric patients with minimal adverse effects 3
  • Iron sucrose: Effective alternative for children who cannot tolerate oral preparations 5

Special Populations

• End-Stage Renal Disease (ESRD):

  • IV iron sucrose is recommended as first-line for ESRD patients with ferritin < 200 ng/mL and transferrin saturation < 20% 2

• Children:

  • Iron therapy should be the first-line treatment for children with low iron stores 2, 6
  • Average dose of IV iron sucrose of 3.6 mg/kg has been used successfully 5

Monitoring and Follow-up

• Reassess iron parameters 8-12 weeks after initiating therapy
• Monitor for clinical improvement in PLMD symptoms
• Consider polysomnography to objectively assess improvement in periodic limb movements during sleep

Common Pitfalls to Avoid

1. Failure to test iron parameters: Many clinicians overlook iron deficiency as a treatable cause of PLMD
2. Inadequate dosing: Using general population iron thresholds rather than the higher thresholds recommended for PLMD
3. Premature discontinuation: Iron therapy may need to be continued long-term to maintain adequate iron stores
4. Overlooking comorbidities: Address exacerbating factors such as caffeine, alcohol, antihistamines, and untreated sleep apnea 1, 2

Iron deficiency is a common underlying factor in PLMD, and appropriate supplementation based on established parameters can significantly improve symptoms and quality of life for these patients.