| Abstract | We characterized cerebral folate deficiency (CFD) as any neuro-psychiatric condition associated with low spinal fluid (CSF) N5-methyltetrahydrofolate (MTHF) but normal folate status outside the central nervous system (CNS). The commonest cause underlying CFD syndromes is the presence of serum autoantibodies of the blocking type directed against folate receptor-? (FR?) attached to the plasma-side of choroid plexus epithelial cells. Blocking FR antibodies inhibit MTHF transport across the choroid plexus. Serum titers of FR antibodies may fluctuate significantly over time. Less frequent causes of CFD are FOLR-1 mutations, mitochondrial disorders and inborn errors affecting folate metabolism. Maternal FR antibodies have been associated with neural tube defects while the presence of FR antibodies in either one or both parents increases the risk of an offspring with infantile autism. Recognizable CFD syndromes attributed to FR-antibodies in childhood are infantile-onset CFD presenting 4-6 months after birth, infantile autism with neurological deficits, and a spastic ataxic syndrome from the age of 1 year, while progressive dystonic or schizophrenic syndromes develop during adolescence. FR autoantibodies are frequently found in autism spectrum disorders, in an Aicardi-Goutières variant and in Rett syndrome. The heterogeneous phenotype of CFD syndromes might be determined by different ages of onset and periods when FR autoantibodies are generated with consequent CNS folate deficiency. Folate deficiency during various critical stages of fetal and infantile development affects structural and functional refinement of the brain. Awareness of CFD syndromes should lead to early detection, diagnosis and improved prognosis of these potentially treatable group of autoimmune and genetically determined conditions. |
| Abstract | Multiple factors such as genetic and extraneous causes (drugs, toxins, adverse psychological events) contribute to neuro-psychiatric conditions. In a subgroup of these disorders, systemic folate deficiency has been associated with macrocytic anemia and neuropsychiatric phenotypes. In some of these, despite normal systemic levels, folate transport to the brain is impaired in the so-called cerebral folate deficiency (CFD) syndromes presenting as developmental and psychiatric disorders. These include infantile-onset CFD syndrome, infantile autism with or without neurologic deficits, a spastic-ataxic syndrome and intractable epilepsy in young children expanding to refractory schizophrenia in adolescents, and finally treatment-resistant major depression in adults. Folate receptor alpha (FR?) autoimmunity with low CSF N(5)-methyl-tetrahydrofolate (MTHF) underlies most CFD syndromes, whereas FR? gene abnormalities and mitochondrial gene defects are rarely found. The age at which FR? antibodies of the blocking type emerge, determines the clinical phenotype. Infantile CFD syndrome and autism with neurological deficits tend to be characterized by elevated FR? antibody titers and low CSF MTHF. In contrast, in infantile autism and intractable schizophrenia, abnormal behavioral signs and symptoms may wax and wane with fluctuating FR? antibody titers over time accompanied by cycling changes in CSF folate, tetrahydrobiopterin (BH4) and neurotransmitter metabolites ranging between low and normal levels. We propose a hypothetical model explaining the pathogenesis of schizophrenia. Based on findings from clinical, genetic, spinal fluid and MRI spectroscopic studies, we discuss the neurochemical changes associated with these disorders, metabolic and regulatory pathways, synthesis and catabolism of neurotransmitters, and the impact of oxidative stress on the pathogenesis of these conditions. A diagnostic algorithm and therapeutic regimens using high dose folinic acid, corticosteroids and milk-free diet is presented which has proven to be beneficial in providing adequate folate to the brain and decreasing the FR? autoantibody titer in those positive for the antibody. |