Very rare novel DHDDS mutation of infant with severe mental-motor retardation, resistant epilepsy, movement disorder

Introduction: The cisPTase enzyme, which plays an important role in dolichol-dependent protein glycosylation, is encoded by the DHDDS gene. Variations or disruptions in protein glycosylation can cause changes in protein structure and function. It has been shown that both biallelic and monoallelic mutations detected in the DHDDS gene cause neurodevelopmental retardation, seizure, and movement disorders. A case of resistant epilepsy with severe mental-motor retardation in a two-year-old male patient with a c.425C>T p.Thr142Met homozygous mutation in the DHDDS gene is presented. Case: The patient, who was born uneventfully as the first child of parents who were married to 2nd-degree cousins, had a focal motor seizure when he was 3 months old. At the age of 9 months, a hyperkinetic movement disorder with more prominent stereotyped hand movements started. In his physical examination, he can only make sounds, no head control, choreoathetosis, stereotypical hand movements, and myoclonus were observed. Deep tendon reflexes were normal. Despite three different antiepileptic drugs, there were focal seizures up to 20 per day. Conclusion: With these features, our patient was the patient with such a severe course at the youngest age with mutations in the DHDDS gene.
Keywords: DHDDS, epilepsy, movement disorder