We have followed up a patient with 8q24.2 --> qter and 15q14 --> pter duplication due to a maternal reciprocal translocation, a condition related to Prader-Willi Syndrome. Apart from dysmorphic features, the patient suffered from recurring episodes of bipolar psychosis. Interestingly, PET scanning revealed revealed prominent bilateral hypometabolism in the frontal, temporal, and parietal lobes as well as in the cerebellum. Possible implications of this rare chromosomal abnormality with regards to psychiatric disorders are discussed, with emphasis on recent evidence suggesting chromosome 15q13-15 as a susceptibility locus for psychosis.