This Publication Is Searchable The Merck Manual of Diagnosis and Therapy Section 19. Pediatrics Chapter 274.
Autism is two to four times more common in boys than girls.
The concordance rate is significantly greater in monozygotic than dizygotic twins, indicating the importance of genetic factors. The syndrome is defined by its behavioral manifestations. The level of intellectual function and the presence or absence of neurologic damage are recorded separately using a multiaxial diagnostic system. CT scans have isolated a subgroup of autistic children with enlarged ventricles, and MRI has recently identified a subgroup of autistic adults with hypoplasia of the cerebellar vermis. Individual cases of autism have been associated with the congenital rubella syndrome, cytomegalic inclusion disease, phenylketonuria, and the fragile X syndrome.