• Loss of social skills
• Loss of bowel and bladder control
• Loss of expressive or receptive language
• Loss of motor skills
• Lack of play
• Failure to develop peer relationships
• Impairment in nonverbal behaviors
• Delay or lack of spoken language
• Inability to start or sustain a conversation

This disorder must be differentiated from both childhood schizophrenia and pervasive developmental disorder (autism).

The most important signs of childhood disintegrative disorder are loss of developmental milestones. The child tends to have normal development through age 3 to 4 and then over a few months undergoes a gradual loss of previously established abilities (e.g., language, motor, or social skills). Generally, the diagnosis is made with a loss of functioning in at least two areas described above.