Objectives: To study the natural history and progression of neurodegeneration in individuals with glycosphingolipid storage disorders (GSL), GM1 and GM2 gangliosidosis, and glycoprotein (GP) disorders including sialidosis and galactosialidosis using clinical evaluation of patients and patient/parent surveys. To develop sensitive tools for monitoring disease progression. To identify biological markers in blood, cerebrospinal fluid, and urine that correlate with disease severity and progression and can be used as outcome measures for future clinical trials. To further understand and characterize the mechanisms of neurodegeneration in GSL and GP storage disorders across the spectrum of disease beginning with ganglioside storage in fetal life. Endpoints: Exploring the natural history of Lysosomal Storage Diseases and Glycoprotein Disorders Study Population: Patients with enzyme or DNA confirmed GM1 or GM2 gangliosidosis, sialidosis or galactosialidosis. Accrual ceiling is 200 participants. No exclusions based on age, gender, demographic group, or demographic location. Patients included in our study are those that are seen at the NIH Clinical Center, subjects that have only sent in blood samples, as well as those who complete the questionnaire or provided head circumference measures. ...