1 out of every 70000 kids born is affected by hyperglycinemia or non-ketotic hyperglycinemia (NKH). This rare disease also goes by the name of glycine encephalopathy, as it is more descriptive of the clinical symptoms. Being so rare, it is also the second-most common disorder of amino acid metabolism after phenylketonuria. It is an inborn error of glycine metabolism, and it affects children at the neonatal stage.
Drake, Joe, Elliot, and Lucas, along with other unfortunate kids, have been living with hyperglycinemia. They and their families have been strong fighters in the face of this awful disease. Parents of these kids have started foundations to fund the only three researchers in the world who are researching nonketotic hyperglycemia (NKH) so that they can find some treatment for their kids.
Hyperglycinemia is the increase of a non-essential amino acid called glycine in the blood, plasma, and CSF. High levels of glycine, especially in the CSF, cause neurological defects as glycine inhibits neurotransmitters, causing cognitive impairment, mental retardation, and overall faulty development in such children. They are left with sudden and frequent myoclonic seizures, which are accompanied by periodic hiccups that remain for a long time and are very pronounced. Some other symptoms for clinical diagnosis include lethargy, difficulty breathing, coma, apnea, low muscle tone, no head control, etc. Patients are kept in the NICU on ventilators if they have severe difficulty breathing. Sometimes they also end up having respiratory arrest. Mental retardation makes them very less receptive and responsive to the stimulus around them. They have a hard time coordinating their body parts and having a general balance.
This disease is classified into two classes, namely severe and attenuated.
Severe NKH in infants starts between 2 weeks and 3 months and there is no developmental progress, whereas attenuated NKH is the one in which the onset of disease starts at 3 months of age with variable developmental progress.
Due to mutations in genes (GLDC and AMT) that get translated to form subunit proteins of the glycine cleavage enzyme, the enzyme does not get produced in sufficient amounts in the body. This results in very little breakdown of glycine. This glycine accumulates in blood, plasma, and CSF. The normal range of glycine in the body varies with age. Infants have a higher level of glycine in their system than older children or people, but even higher levels of glycine in the system cause the problem.
This autosomal recessive metabolic disorder has no treatments that can cure it; it can only be managed through some drugs like sodium benzoate, dextromethorphan, and some traditional therapies. Some of these therapies have been helping those in distress. These include cold laser therapy, movement lessons, neurotherapies, CBD, and some others. Movement lessons given in water help the children beat some amount of gravity, and it helps them. Though the families are managing the NKH well and with a strong heart, statistics suggest that children affected by it do not live past 5 years of age. Research related to its treatment and epidemiology is going on, and we hope for a better world where no child would die because of the absence of treatment.