Most children with AP-4-associated HSP have:
• A “floppy” appearance in infancy due to low muscle tone
• Increasing spasticity and paralysis in the lower limbs starting in early childhood
• Delayed motor development
• Poor or absent speech development
• Moderate to severe intellectual disability
• Microcephaly
• Seizures including frequent seizures in the setting of fever
Other known features of AP-4-HSP can include the following (not every child will have these features):
• Short stature
• Dystonia (involuntary muscle contractions)
• Ataxia (impaired balance and coordination)