An Infant With Movement Disorder And Infantile Spasm: Attenuated NKH

Objectives:Nonketotic hyperglycinaemia (NKH) is a autosomal recessive disease due to a defect in the glycine cleavage system. Based on ultimate outcome NKH is categorized into severe NKH and attenuated NKH. Case Report:A 7-month-old girl presented with epileptic spasms. The patient was moderately microcephalic and had iris coloboma. Seizures started when the patient was around 6-months old. Despite being a moderate hypotonic infant until that point, she had been developing almost in line with her age, except in the motor area. Her seizures began as brief and focal, then progressed to infantile spasms. Her EEG was consistent with hypsarrhythmia. Her seizures were under control with two anti-seizure medications. The patient had choreatotic movements besides seizures. In the brain MRI of the patient, cerebellar and cerebral volume loss, restricted diffusion were observed. There was no cortical malformations. A high serum glycine levels were determined. In the genetic analysis, in GLDC gene a missense homozygous variant detected. This mutation compatible with glycine encephalopathy (non-ketotic hyperglycinaemia). The patient started on a ketogenic diet, sodium benzoate, and dexmethorphan therapy. Under this treatment, her movement disorder is highly controlled, as is her epilepsy. Conclusions:The clinical spectrum may be broad in inborn errors of metabolism. Early treatment is associated with a good outcome, especially in the treatable ones. Patients with attenuated forms of NKH may have easy controlled epilepsy, choreic movements, hyperactivity, variable degrees of devolepmental delays, episodes of severe lethargy. Drawing attention to attenuated forms of NKH,whose classical form is a well-known condition, would be rewarding.
Keywords: Nonketotic hyperglycinaemia, attenuated NKH, movement disorder