Observation of two patients with Phelan-McDermid syndrome (22q13.3 microdeletions of the SHANK3 gene) within 10—12 years allowed us to describe the clinical pathomorphism of psychotic episodes with violation of consciousness and catatonic symptoms in adolescence with autism spectrum disorders (ASD). The described phenotypes were characterized by intellectual disability, general speech underdevelopment, muscle hypotonia and developmental dyspraxia. Their causal relationships with epileptic encephalopathy, schizophrenia, bipolar and hyperkinetic disorders have been analyzed.

The therapeutic efficacy of combination therapy with aripiprazole and benzodiazepines (clonazepam/diazepam) allowed qualifying psychotic episodes as pediatric delirium.

The significant clinical efficacy of lithium and lamotrigine in the described patients was consistent with the hypothesis that microdeletion of the SHANK3 gene may be associated with bipolar disorder. Treatment of acute psychotic disorders with lithium salt was effective in both patients but had limitations due to poor tolerance in the long-term use.

The combination of lithium and lamotrigine may be recommended for the treatment of polymorbid mental disorders in patients with SHANK3 encephalopathies. If lithium salts are poorly tolerated, a combination of lamotrigine and aripiprazole may be used.