Note that the phenotypic spectrum of USP7 mutations is still being uncovered, and not all individuals with a HAFOUS present these features, but main characteristics include:
- Developmental delay/intellectual disability
- Autism spectrum disorder
- Epilepsy
- Abnormal brain MRI
- Speech/motor impairments (some patients being completely non-verbal)
- Neonatal hypotonia
- Feeding problems
- Joint contractures
- Hypogonadism
- Eye problems (strabismus, myopia, or nystagmus)
- Short stature
- Difficulty gaining weight
- Gastrointestinal issues (reflux/GERD, chronic constipation, or chronic diarrhea)