Hyperglycinemia, isolated nonketotic type 2

Isolated Nonketotic Hyperglycinemia Type 2 (INH Type 2) is a rare genetic disorder characterized by an elevated level of glycine in the body due to a specific enzyme deficiency. This condition is part of a broader group of disorders known as amino acid disorders, which affect the body's ability to break down and utilize amino acids properly. Unlike the more common form, Nonketotic Hyperglycinemia (NKH), which presents with severe neurological symptoms shortly after birth, INH Type 2 has a different onset and clinical presentation.

Causes

INH Type 2 is caused by mutations in the gene responsible for the production of a particular enzyme involved in the glycine cleavage system. This enzyme's deficiency leads to an accumulation of glycine in the body, particularly affecting the brain and spinal cord, where glycine acts as a neurotransmitter. The genetic mutations are inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected by the disorder.

Symptoms

The symptoms of INH Type 2 can vary widely among affected individuals. Unlike the classic form of NKH, symptoms may not be evident at birth and can range from mild to severe. They may include developmental delay, intellectual disability, seizures, and hypotonia (reduced muscle tone). The variability in symptoms often leads to challenges in early diagnosis.

Diagnosis

Diagnosis of INH Type 2 involves a combination of clinical evaluation and laboratory tests. Elevated levels of glycine in the blood (hyperglycinemia) and cerebrospinal fluid (CSF) without the presence of ketones are indicative of the condition. Genetic testing can confirm the diagnosis by identifying mutations in the specific gene associated with the disorder.

Treatment

Treatment for INH Type 2 is symptomatic and supportive. Management strategies may include dietary modifications to limit glycine intake, medications to control seizures, and interventions to support development and mobility. There is currently no cure for INH Type 2, and the focus is on improving quality of life and minimizing symptoms.

Prognosis

The prognosis for individuals with INH Type 2 varies depending on the severity of symptoms and the effectiveness of management strategies. Early intervention and tailored treatment plans can improve outcomes for some individuals.

This metabolic pathology related article is a stub. You can help WikiMD by expanding it.