The purpose of a Natural History Study of AspartylglucosaminuriaA rare neurodegenerative lysosomal storage disease (LSD) characterized by developmental delay, psychomotor regression, worsening intellectual disability, gait disturbance, and shortened lifespan. There are currently no available treatments for AGU. (AGU) is to better understand AGU. It aims to:

• Understand and document the medical history, clinical characteristics, progression of symptoms, and medical events in individuals with AGU.
• Provide greater understanding of AGU by determining outcome measures or a desired solution that a potential therapy could provide for use in future clinical trials.