Treating Leg Symptoms in Women With X-linked Adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a neurodegenerative disease caused by mutations in the ABCD1 peroxisomal half-transporter gene, resulting in accumulation of very long chain fatty acids (VLCFAs). As ALD is an X-linked disease, women were previously considered asymptomatic carriers. It is now known that even though adrenal insufficiency and cerebral disease occur in less than 1% of women, more than 80% eventually develop progressive spinal cord disease. Recently, the investigators observed that women are more frequently affected by movement disorders independent of the demyelinating brain disease seen in men. In a pilot study, the investigators found that up to 25% of women with ALD have moderate to severe Restless Leg Syndrome (RLS). RLS is a movement disorder characterized by a powerful urge to move the legs, usually accompanied by unpleasant dysesthesias, that is precipitated by rest, relieved by movement, and most pronounced in the evening or at night. Dopamine agonists such as pramipexole are efficacious and first-line FDA-approved treatments in low doses for primary (i.e., idiopathic) RLS and have been shown to improve both the primary symptoms of RLS (sensory discomfort, motor restlessness) as well as the associated sleep and quality of life impairments in RLS.

In the first phase of the study, the investigators will enroll 100 women with ALD at the two participating sites (Massachusetts General Hospital and University Medical Center Amsterdam). Participants will undergo structured phone interviews with both an expert in ALD and RLS to assess the presence of probable or definite RLS. Participants with probable or definite RLS will then undergo an additional phone call to determine RLS severity and assess eligibility for the second phase of the study. The objective of the first phase of the study is to determine the prevalence of RLS in women with ALD.

The second phase of the study will consist of a 4-month randomized, double-blind, placebo-controlled cross over study to assess whether pramipexole improves RLS symptoms as well as sleep and gait measures in women with ALD. The investigators will enroll 24 women with ALD and moderate to severe RLS. Participants will first be randomized 1:1 to 0.125-0.5 mg pramipexole or placebo. After the first two months, a switch-over visit will take place and include a battery of neurological assessments, walking measures, polysomnography, and questionnaires. At this visit, the crossover from pramipexole to placebo and from placebo to pramipexole will occur. The final study visit will occur 2 months after the switch-over visit and all study assessments will be repeated.