CTX is typically a highly progressive disease, with case reports of symptoms that first appear at any time from birth through adulthood and then worsen over time. Because idiopathic bilateral cataracts occur at an early age in many children with CTX, biomarker testing of these children presents an opportunity for diagnosing children with CTX. Eligible participants will be asked to give a small blood sample and urine sample, and may have genetic testing done to see if they have the gene for CTX. This study will take place on 1 visit for approximately 30 minutes.