FOLR1 deficiency feat: psychomotor decline, epilepsy with drop attacks, progressive movement disorder, hypomyelination. MTHFR deficiency feat: developmental delay, hypotonia, apnea, epilepsy, thrombosis, brain atrophy. DHFR deficiency feat: megaloblastic anemia, seizures. Serine biosynthesis disorders feat: Microcephaly, developmental delay, spasticity, seizures, neuropathy, ichthyosis. The gene discussed is DHFR; the disease is ichthyosis.