A Case of Cerebral Folate Deficiency due to FOLR1 Mutation in a 10-Year-Old Girl: Clinical Presentation and Treatment Outcomes.

Cerebral folate deficiency (CFD) is characterized by reduced levels of folate, particularly 5-methyltetrahydrofolate (5-MTHF), in the cerebrospinal fluid (CSF). This case report describes a 10-year-old girl diagnosed with CFD due to a pathogenic mutation in the FOLR1 gene, which impairs folate transport across the blood-brain barrier. The patient, who exhibited normal early development, experienced developmental regression and refractory seizures after the age of four. Despite treatment with multiple antiepileptic medications, her seizures remained uncontrolled. Genetic testing via whole exome sequencing confirmed the FOLR1 mutation, leading to the initiation of folinic acid supplementation. Following treatment, the patient demonstrated significant clinical improvement. This case underscores the critical role of genetic testing in diagnosing CFD and guiding effective treatment strategies, including the timely use of folinic acid to mitigate neurological deficits associated with folate transport impairments.