Table 1.

The list of differential diagnosis with Rett syndrome.

Stage I Developmental arrest (typically in children 6–18 months of age)	Stage II Rapid deterioration or regression (typically in children 1–4 years of age)	Stage III Pseudostationary (typically in children 2–10 years of age)	Stage IV Late motor deterioration (typically in patients > 10 years)
Benign congenital hypotonia	Autism	Spastic ataxia	Other degenerative disorders
Cerebral palsy	Angelman syndrome	Cerebral palsy
Prader–Willi syndrome	Encephalitis	Spinocerebellar
Metabolic disorders (e.g., fetal alcohol syndrome, trisomy 13)	Hearing and/or visual disturbance	degeneration
	Landau–Kleffner syndrome	Leukodystrophies
	Psychoses	Neuroaxonal dystrophy
	Slow virus	Lennox–Gastaut syndrome
	Panencephalopathy	Angelman syndrome (likely not Kabuki because patients would have macrocephaly)
	Tuberous sclerosis
	Metabolic disorders (e.g., phenylketonuria, ornithine transcarbamylase deficiency)
	Infantile neuronal ceroid lipofuscinosis