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 NICE CKS. Primary RLS is diagnosed when no identifiable underlying cause is found NICE CKS.

• Iron Deficiency: A common secondary cause of RLS is iron deficiency anaemia, or a serum ferritin level less than 50–75 micrograms/L NICE CKS. It is crucial to investigate the cause of iron deficiency and prescribe iron supplements, often with vitamin C to aid absorption NICE CKS. 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 NICE CKS. 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 NICE CKS. Drug treatment for RLS is generally not recommended during pregnancy or breastfeeding NICE CKS.
• Other Medical Conditions:
  • Neurological Conditions: RLS can be a non-motor symptom in conditions like Parkinson's disease NICE NG71. 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 NICE NG127. Isolated tingling not associated with nerve compression in children also warrants neurological assessment NICE NG127.
  • Sleep Disorders: Obstructive sleep apnoea can impact sleep quality and should be considered in the assessment of RLS NICE CKS.
  • 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 NICE NG62. If the cause of sleep disturbance, pain, discomfort, or distress is unclear after routine assessment, referral for a specialist multidisciplinary team assessment is recommended NICE NG62.

The approach to differentiation involves addressing these underlying causes NICE CKS. 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 NICE CKS.