Cerebral folate deficiency syndrome.

to the editor: Ramaekers et al. (May 12 issue)1 report 28 patients with the cerebral folate deficiency syndrome characterized by decreased levels of 5-methyltetrahydrofolate (5MTHF) in the cerebrospinal fluid caused by autoantibodies’ blocking of folate transport into the brain. The patients benefited from folinic acid supplementation. The clinical features of this syndrome fit with other neurodegenerative disorders. According to previous papers by the authors, the latter disorders can be associated with cerebral folate deficiency as a secondary phenomenon.2-4 Patients with secondary cerebral folate deficiency (e.g., the Rett syndrome) potentially benefit from folinic acid supplementation.2-4 The authors do not report the presence or absence of folate-receptor autoantibodies in secondary cerebral folate deficiency. Before claiming that the cerebral folate deficiency syndrome is a separate entity, the investigators should demonstrate that it is a unique, autoantibody-mediated disease, different from secondary cerebral folate deficiency.