Pathogenic variants in the IRF2BPL gene are associated with neurodevelopmental disorders with varying degrees of regression, loss of speech and epilepsy. The phenotype is also known as Neurodevelopmental Disorder with regression, Abnormal Movements, loss of Speech, and Seizures (NEDAMSS). The motor symptoms of this disorder share significant phenotypical characteristics with catatonia, a severe neuropsychiatric psychomotor syndrome. The objective of this article is to expand the knowledge on the presentation of NEDAMSS with a focus on psychiatric symptoms including catatonia. A systematic review of 32 case presentations of NEDAMSS, and a novel case report of a patient with NEDAMSS, exhibiting multiple psychiatric symptoms, including catatonia are presented. Psychiatric symptoms and disorders including affective disorders, psychotic symptoms, catatonia, and developmental disorders are reported in one third of the reviewed cases. Reported effects of pharmacological treatment on motor symptoms of NEDAMSS are very limited. Our case presents improvement in motor symptoms originally attributed to NEDAMSS, after treatment with Lorazepam following diagnosis with catatonia. Patients with NEDAMSS may present with both neurological and psychiatric symptoms. The clinical presentation of NEDAMSS motor symptoms and catatonia have similarities and thus poses significant challenges to the diagnostic process, with risk of incorrect or delayed treatment. The limited experience and the complex phenotype of NEDAMSS complicates pharmacological treatment and encourages caution, especially with the use of antipsychotic drugs in the presence of possible catatonic symptoms.