Which of the following is a characteristic of childhood disintegrative disorder?

Childhood disintegrative disorder, also known as Heller's syndrome, is characterized by normal development in the first few years of life, followed by a marked regression in multiple areas of functioning after the age of two. Children typically show a significant loss of previously acquired skills, including language, social, and motor skills, between the ages of two and ten. This regression is what makes behavioral conditions developing within this age range a hallmark of the disorder.

The correct answer reflects this critical aspect of the disorder, emphasizing that the onset of behavioral issues occurs after a period of normal development. In contrast, the other choices do not accurately depict the nature of childhood disintegrative disorder. For instance, developmental delays starting at birth pertain more to different conditions and do not align with the typical trajectory of a child with this disorder, who initially develops normally. A lifelong diagnosis without fluctuations does not capture the reality of childhood disintegrative disorder, where children experience significant changes in their capabilities. Lastly, the notion of social skills developing at an accelerated pace is not representative, as children with this disorder often experience a decline in social functioning rather than improvement.