Cerebral folate deficiency due to folate receptor autoantibodies is a common condition in autism spectrum disorders[1]. In this condition, autoantibodies block folate from crossing the blood brain barrier via the FRα, resulting in normal blood level of folate but folate deficiency in the brain. [2]
A blood test for this condition is available through http://iliadneuro.com/order-a-kit.html ([3]). However, to verify cerebral folate deficiency one would need a lumbar puncture to measure cerebrospinal fluid levels of methylfolate. It is sometimes preferred to trial a treatment for cerebral folate deficiency in children with autism spectrum disorders without first confirming low cerebrospinal fluid methylfolate.
Treatment involves a strict milk-free diet to reduce folate receptor autoantibody levels [4] and an extremely high dose of folinic acid which bypasses blocked receptors. Treatment has shown to be effective in improving language and adaptive skills in children with ASD. [5], [6]