For example, the typical clinical phenotypes of Salla disease (SD; OMIM: #604369) caused by SLC17A5 mutations are hypotonia, ataxia, nystagmus, epilepsy, and findings of cerebral and cerebellar atrophy accompanied by an elevation of free urinary sialic acid [11]. The gene discussed is SLC17A5; the disease is free sialic acid storage disease.