Salla disease is a disorder of free sialic acid metabolism. These neurodegenerative disorders resulting from increased lysosomal storage of free sialic acid. The mildest phenotype is Salla disease, characterized by normal appearance and neurologic findings at birth followed by slowly progressive neurologic deterioration resulting in mild-to- moderate psychomotor retardation, spasticity, athetosis, and epileptic seizures. The free sialic acid storage disorders are inherited in an autosomal recessive manner due to mutations in the SLC17A5 gene.