Sjogren-Larsson syndrome (SLS) is a rare genetic disease in which patients typically exhibit ichthyosis (dry, scaly skin), intellectual disability, spasticity, seizures and a distinctive maculopathy. The purpose of this study is to define the clinical spectrum and natural history of Sjogren-Larsson syndrome, and identify biomarkers that correlate with disease phenotype while establishing a registry for future investigations of biochemical pathogenesis and therapy.