Prior to the discovery of a genetic cause,<unk>  had been designated as a pervasive developmental disorder by the Diagnostic and Statistical Manual of Mental Disorders (DSM), together with the autism spectrum disorders. Some argued against this conclusive assignment because<unk>  resembles non-autistic disorders such as fragile X syndrome, tuberous sclerosis, or Down syndrome that also exhibit autistic features. After research proved the molecular mechanism, in 2013 the DSM-5 removed the syndrome altogether from classification as a mental disorder.<unk>  diagnosis involves close observation of the child's growth and development to observe any abnormalities in regards to developmental milestones. A diagnosis is considered when decreased head growth is observed. Conditions with similar symptoms must first be ruled out. There is a certain criteria that must be met for the diagnosis. A blood test can rule in or rule out the presence of the MECP2 mutation, however, this mutation is present in other conditions as well. For a classic diagnosis, all four criteria for ruling in a diagnosis must be met, as well as the two criteria for ruling out a diagnosis. Supportive criteria may also be present, but are not required for diagnosis. For an atypical or variant diagnosis, at least two of the four criteria for ruling in the diagnosis must be met, as well as five of the eleven supportive criteria. A period of symptom regression followed by recovery or symptom stabilization must also occur. Children are often misdiagnosed as having autism, cerebral palsy, or another form of developmental delay. A positive test for the MECP2 mutation is not enough to make a diagnosis. Ruling in * Decreased or loss of use of fine motor skills * Decreased or loss of verbal speech * Abnormalities during gait * Repetitive hand movements such as wringing/squeezing or clapping/tapping Ruling out * Traumatic or anoxic/hypoxic brain injury, neurometabolic disease, or severe infection that may better explain symptoms * Abnormal psychomotor development during the first six months of life Supportive criteria * Breathing disturbances when awake * Bruxism while awake * Impaired sleep pattern * Abnormal muscle tone * Peripheral vasomotor disturbances * Scoliosis/kyphosis * Growth retardation * Small cold hands and feet * Inappropriate laughing/screaming spells * Diminished response to pain * Intense eye communication (eye pointing) Differential diagnosis Signs of<unk>  that are similar to autism: Signs of<unk>  that are also present in cerebral palsy (regression of the type seen in<unk>  would be unusual in cerebral palsy; this confusion could rarely be made):
Rett syndrome
1p36 deletion syndrome
Fragile X syndrome
Angelman syndrome
Poland syndrome
Childhood disintegrative disorder
Fragile X-associated tremor/ataxia syndrome
Snyder–Robinson syndrome