Elevated homocysteine and N-methyl-d-aspartate-receptor antibodies as a cause of behavioural and cognitive decline in 22q11.2 deletion syndrome.

A 19-year-old male with 22q11.2 deletion syndrome presented with a 4-year history of cognitive decline and symptoms suggestive of atypical psychosis. Potential for elevated homocysteine and NMDA-receptor antibodies in the pathogenesis of his symptoms was investigated. He had elevated blood homocysteine level (18.7 μmol/l), low-normal vitamin B12 and folate levels and was positive for NMDA-receptor antibodies. Treatment with daily folinic acid (0.8 mg) and vitamin B12 (1 mg) led to dramatic improvement in his cognitive and behavioural presentation. Subsequent plasma exchange resulted in a further, significant clinical improvement. Homocysteine levels and NMDA-R antibodies should be investigated as potential causes of behavioural and cognitive symptoms in patients with 22q11.2 deletion syndrome.