Autism spectrum disorders (ASD) are developmental disorders that present with impaired social interactions/communications and repetitive patterns of language and behavior. The severity can range from very impaired (with severe intellectual disability and little or no language) to average or superior intellectual function and typical verbal language skills.
Irritability and temper outbursts aren't uncommon symptoms in children with ASD, related to many factors, including the following:
Rigid/inflexible thinking and behaviors
Difficulties with self-expression
Impaired social interactions and relationships
Additionally, anxiety is a common co-occurrence in ASD, which can cause moodiness and temper outbursts sometimes seen in bipolar disorder. ADHD may also be present in kids with ASD, and depression can occur more frequently than in children without ASD.
More severe presentations of ASD are usually diagnosed early in life, but children with less severe symptoms can be harder to accurately diagnose. If mood symptoms are especially pronounced, especially in young children, these symptoms may become a target of evaluation and treatment, and the ASD diagnosis may be missed or less clear-cut. Identifying these conditions is important, because the care and support include many features that aren't necessarily needed in bipolar disorder, such as speech/language therapy and other interventions to address the core symptoms of ASD.