Autism spectrum disorder without disorder of intellectual development and with absence of functional language with loss of previously acquired skills (Q98648)

All definitional requirements for autism spectrum disorder are met, intellectual functioning and adaptive behaviour are found to be at least within the average range (approximately greater than the 2.3rd percentile), and there is complete, or almost complete, absence of ability relative to the individual’s age to use functional language (spoken or signed) for instrumental purposes, such as to express personal needs and desires. In addition, the individual’s clinical history includes a loss of previously acquired skills, most commonly the loss of language and social skills during the second year of life. Loss of previously acquired skills is rare after three years of age, and when it occurs is more likely to involve cognitive and adaptive skills (e.g., loss of bowel and bladder control, impaired sleep) and to present together with increasing emotional and behavioural disturbance.