Autosomal recessive spastic paraplegia type 61 (SPG61) is a rare, inherited neurological disorder characterized by progressive muscle weakness and stiffness (spasticity) in the legs. It is caused by mutations in the KIF5A gene, which is involved in the transport of proteins within cells. Symptoms usually begin in childhood or adolescence and may include difficulty walking, muscle spasms, and difficulty with balance and coordination. In some cases, the disorder may also affect the arms and hands. There is currently no cure for SPG61, but physical therapy and medications may help to manage symptoms.