A 4-year-old girl who is an only child stas school. He has never shown much of an interest in interacting with others. He has never used many words which the parents attribute to his isolation as an only child. They tell the teacher he has always done best with a strict schedule and doesn't tolerate changes well. Other children attempt to play with him but his response is to either ignore them or get angry at their advances. The patient described can best be distinguished from Rett disorder because of which of the following?
Autism and Rett's disorder show evidence of presence prior to the age of 36 months. However, in Rett disorder, the child has an early phase of normal development then gradually loses those skills toward fuher decline. The Rett's syndrome is usually marked by withdrawn behavior that simulates autism, dementia, ataxia, loss of purposeful hand movements, and respiratory irregularities. This is a hereditary form of mental retardation, but one that affects girls. The responsible spontaneous mutation has been shown to relate to a defect at chromosomal site Xq28, making it one of the X-linked mental retardations. Highly characteristic is a period of 6 to 18 months of normal development followed by the rapid appearance and progression of all these signs, and then by relative stability for decades. Spasticity, muscle wasting, scoliosis, and lower limb deformities may become evident in the late stages of the illness. Handwringing and similar stereotypes are very typical features (and are different in subtle ways from the hand-flapping of autistic children). Ref: Ropper A.H., Samuels M.A. (2009). Chapter 38. Developmental Diseases of the Nervous System. In A.H. Ropper, M.A. Samuels (Eds), Adams and Victor's Principles of Neurology, 9e.
Social difficulties
Lack of language development
Absence of a period of normal development
Evidence of mental retardation