Disturbed serine metabolism and psychosis in a patient with a de novo translocation (2;10)(p23;q22.1).

Psychiatric diagnosing in mentally retarded patients is notoriously difficult and routine application of current taxonomies is of very limited use. Although psychotic disorders in general can be satisfactory grouped on a descriptive level, the aetiology is most probably very heterogeneous. In this case report a female patient is described who presented with mild mental retardation and recurrent affective psychotic episodes. Chromosome analysis showed a female karyotype with a de novo translocation (2;10)(p23;q22.1). Biochemical evaluation demonstrated a persistently increased taurine and decreased methionine in plasma, suggesting a disturbed one-carbon metabolism. Treatment with risperidone in combination with valproic acid resulted in prevention of further relapses and stabilisation of mood. An imbalance of chromosomes 2 and 10 was excluded by array CGH. A disruption of the PCBD gene could not be demonstrated by FISH.