A case of 5,10-methenyltetrahydrofolate synthetase deficiency due to biallelic null mutations with novel findings of elevated neopterin and macrocytic anemia

Abstract

We describe a case of 5,10-methenyltetrahydrofolate synthetase (MTHFS) deficiency characterized by microcephaly, global developmental delay, epilepsy, and cerebral hypomyelination. Whole exome sequencing (WES) demonstrated homozygosity for the R74X mutation in the MTHFS gene. The patient had the unexpected finding of elevated cerebrospinal fluid (CSF) neopterin. The novel finding of macrocytic anemia in this patient may provide a clue to the diagnosis of this rare neurometabolic disorder.