The symptoms include:

• Impaired speech
• Ataxia
• Scoliosis- curvature of the spinal cord
• Happy and excitable
• Seizures and convulsions beginning at age 2
• Have reduced sleeping time compared to other children
• Short attention span
• Frequently sticking out the tongue
• Hair, skin, eyes are pale

Common symptoms and their severity as reported by people on Patientslikeme.

• The condition is caused by loss of function of UBE3A gene
• This can result from mutation or deletion of the gene.
• It may also occur as a result of inactivation of the gene due to other chromosomal changes.
• In rare cases, a child may inherit two copies of inactive forms of the gene instead of one active and one inactive (uniparental disomy).