Case Series. Nonketotic hyperglycinemia patients with and without a ketogenic diet treatment

Background: Nonketotic hyperglycinemia, autosomal recessive, inborn error of glycine degradation caused by a defect of the glycine cleavage system, This defect causes large quantities of glycine to accumulate in all body tissues, particularly in the central nervous system (CNS). In classical neonatal-onset NKH, excessive CNS glycine levels lead to lethargy, poor feeding, hypotonia, and hiccups that develop within hours to days after birth. Symptoms progress to seizures, apnea, respiratory insufficiency, and coma, and typically lead to death between 3 and 5 months of age. Caused by mutation in the glycine dehydrogenase gene /GLDC), the glycine cleavage system H protein gene (GCSH), and aminomethyltransferase gene (AMT).

Death in infancy common for patients with the classic neonatal form. Patients with atypical form have milder disease, with onset in the first months of life and increased survival. The aim of this case series of patients with NKH produced by the GLDC gene mutation was to perform international classification of functionality in patients with and without a ketogenic diet treatment. Methods: a case series study of four patients was based on a characterization of patients with NKH produced by the GLDC gene mutation. The functionality was evaluated by means of a questionnaire developed from the ICF, evaluating bone structures, functions (swallowing, breathing, attention, muscle tone, strength and others), activities and participation (rolling, sitting, standing, activities of the daily life and others). in patients with and without a ketogenic diet treatment. Results: Differences in functionality according to the International Classification of Functioning (ICF) of patients with nonketotic hyperglycinemia treated with a ketogenic diet and those who were not exposed. Patients without the diet achieved milestones in neuromotor development, such as rolling over and tolerating a supported sitting position, in addition to tolerating the oral swallowing. Discussion/Conclusion: KHN requires early diagnosis and timely management in the first month of life by an interdisciplinary and neurostimulatory team that includes strict glycine-free dietary management to impact prognosis.. Patients on the diet show no potential for neuromotor development. A larger sample size is required to demonstrate the impact of the glycine-free diet vs. the ketogenic diet on patient outcomes.