Study of Disease Progression in Adults With Inherited Forms of Spastic Paraplegia

Progressive weakness and spasticity of the legs are characteristics of numerous disorders and conditions, including those that are inherited neurological disorders. Adrenomyeloneuropathy (AMN) is an example of an inherited form of spastic paraplegia. Adrenoleukodystrophy (ALD) is a progressive neurodegenerative disorder caused by a mutation in the ABCD1 gene localized to the X-chromosome (Xq28). The ABCD1 gene encodes a peroxisomal adenosine triphosphate (ATP) binding cassette transporter responsible for transport of very long chain fatty acids (VLCFA) from the cytosol into the peroxisome for degradation. A mutation in ABCD1 results in reduction in the degradation of the VLCFA by peroxisomal β-oxidation, and saturated VLCFA, in particular C26:0, accumulate in tissues and body fluids (i.e., brain, nervous system, adrenal glands). One of the key clinical symptoms during aging of ALD patients is a slowly progressive axonopathy affecting sensory ascending and motor descending spinal cord tracts with 100% penetrance in men, an ALD phenotype known as AMN. There are no treatment options available, which leaves AMN patients with a progressive disorder that leads to lifelong physical disability. The progressive dying-back axonopathy represents the core clinical feature of AMN, with onset usually between 20 and 30 years of age in male participants. The initial symptoms include progressive stiffness and weakness of the legs, impaired vibration and position senses in the lower limbs, falls, sphincter disturbances and impotence, as well as scarce scalp hair (alopecia). About 66% of male AMN patients have adrenocortical insufficiency (Addison disease). The course of AMN-related disabilities over time is poorly or incompletely understood due to a limited number of patients and lack of treatments. This study will help obtain a better understanding of the progression of disease with AMN and facilitate efficient clinical development of future SwanBio interventional medications.