A Serine Synthesis Defect Presenting With a Charcot-Marie-Tooth-Like Polyneuropathy

Background: Serine synthesis defects, characterized by developmental delay and seizures, have been described in children. Objective: To describe a case of serine synthesis defect due to 3-phosphoglycerate dehydrogenase deficiency in an adult with prominent chronic polyneuropathy. Design: Case report. Setting: Neurologic referral center. Patient: A 31-year-old man with congenital cataracts, mild psychomotor retardation, slight cerebellar ataxia, and chronic axonal sensorimotor polyneuropathy. Interventions: Electrophysiologic, metabolic, and genetic testing and treatment with oral L-serine. Main Outcome Measures: Serine values in plasma and cerebrospinal fluid and clinical examination. Results: Amino acid analysis showed low serine levels in plasma and cerebrospinal fluid, and genetic analysis revealed 2 heterozygous mutations in the PGDH gene. Treatment with high-dose serine resulted in normalization of plasma serine values and subjective functional improvement. Conclusions: This case expands the phenotypic spectrum of 3-phosphoglycerate dehydrogenase deficiency. Plasma amino acid chromatography should be added to the list of investigations performed in patients with Charcot-Marie-Tooth-like polyneuropathy, especially if it is associated with psychomotor delay and congenital cataracts.