The main symptoms are difficulties in communication and social interaction, in addition to the presence of restrictive and repetitive patterns of behavior, specific interests, or sensory regulation difficulties.

Some warning signs are:

• Little eye contact and few social smiles.
• Language development delay.
• When language is involved, it can be literal, with difficulty understanding jokes or double meanings, and also in reciprocal conversation.
• Lack of interest in other children.
• Difficulties with group play.
• They rarely share interests (for example, they don't point to things that catch their attention to share them with another person).
• Limited symbolic play (such as feeding dolls or pretending that the dolls talk).
• They may exhibit tactile, olfactory, or auditory hypersensitivity. Loud noises or certain specific sounds bother them.
• They exhibit unusual or very marked interests in specific topics.
• They may exhibit repetitive behaviors.