Phelan-McDermid syndrome due to mutation in an intellectually disabled adult male: successful treatment with lithium.

For 30 years, Phelan and co-workers described a syndrome characterised by neonatal hypotonia, global developmental delay, strongly impaired speech, sleep disturbances and hyperreactivity to sensory stimuli. This Phelan-McDermid syndrome (PMS), also presenting with symptoms from the autism spectrum and a higher risk of developing seizure disorders, may be caused by a deletion of chromosome 22q13 or by a mutation in the gene. Its core psychopathological phenotype comprises symptoms from the bipolar spectrum for which generally treatment with a mood-stabilising anticonvulsant in combination with an atypical antipsychotic seems to be most effective.