How can I differentiate between primary Restless Legs Syndrome and secondary causes related to other medical conditions?

Differentiating between primary (idiopathic) Restless Legs Syndrome (RLS) and secondary causes involves a thorough assessment to identify and address any underlying conditions or factors that may be precipitating or exacerbating RLS symptoms ¹. Primary RLS is diagnosed when no identifiable underlying cause is found ¹.

• Iron Deficiency: A common secondary cause of RLS is iron deficiency anaemia, or a serum ferritin level less than 50–75 micrograms/L ¹. It is crucial to investigate the cause of iron deficiency and prescribe iron supplements, often with vitamin C to aid absorption ¹. Ferritin levels below 50 micrograms/L have been correlated with increased symptom severity and reduced sleep quality in people with RLS (Oertel, 2007). Iron therapy can improve restlessness and RLS severity compared to placebo (Trotti, 2019).
• Medications: Certain existing drugs can precipitate or exacerbate RLS symptoms ¹. It is important to consider if changing or stopping such medication is an option (Garcia-Borreguero, 2017).
• Pregnancy: RLS symptoms are common during pregnancy and are likely to resolve or improve soon after delivery ¹. Drug treatment for RLS is generally not recommended during pregnancy or breastfeeding ¹.
• Other Medical Conditions:
  • Neurological Conditions: RLS can be a non-motor symptom in conditions like Parkinson's disease ⁴. In children, tingling accompanied by other peripheral nervous system symptoms such as weakness, bladder, or bowel dysfunction may indicate an acute polyneuropathy (e.g., Guillain–Barré syndrome) or other neuro-inflammatory conditions, requiring urgent neurological assessment ². Isolated tingling not associated with nerve compression in children also warrants neurological assessment ².
  • Sleep Disorders: Obstructive sleep apnoea can impact sleep quality and should be considered in the assessment of RLS ¹.
  • Cerebral Palsy: While sleep disturbances are common in children and young people with cerebral palsy, they may be caused by factors such as environment, hunger, or thirst ³. If the cause of sleep disturbance, pain, discomfort, or distress is unclear after routine assessment, referral for a specialist multidisciplinary team assessment is recommended ³.

The approach to differentiation involves addressing these underlying causes ¹. Referral to a specialist, such as a sleep specialist or neurologist, should be considered if there is doubt about the diagnosis or if initial treatment is unsuccessful ¹.