"Mood dysregulation" refers to difficulties in controlling and managing one's emotions. It means that a person has trouble dealing with and expressing their feelings in a healthy and appropriate way.
In the latest edition of the mental disorder diagnostic reference manual, the DSM - 5, children may instead be diagnosed with disruptive mood dysregulation disorder, instead of bipolar disorder. (psychcentral.com)
Also, the criteria are not met for disruptive mood dysregulation disorder. (bpdfamily.com)
Bipolar disorder and disruptive mood dysregulation in children and adolescents: assessment, diagnosis and treatment (ebmh.bmj.com)