Argininemia

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
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Argininemia
Synonyms	Arginase deficiency, Argininemia
Pronounce
Specialty	Medical genetics
Symptoms	Developmental delay, intellectual disability, spasticity, seizures, growth retardation
Complications	N/A
Onset	Infancy to early childhood
Duration	Lifelong
Types	N/A
Causes	Genetic mutation in the ARG1 gene
Risks
Diagnosis	Blood test, urine test, genetic testing
Differential diagnosis	Other urea cycle disorders
Prevention
Treatment	Dietary management, arginine restriction, ammonia scavengers
Medication
Prognosis	Variable, depends on early diagnosis and management
Frequency	Rare, estimated at 1 in 1,000,000
Deaths

Argininemia

Diagram illustrating the urea cycle, highlighting the role of arginase

Argininemia is a rare genetic disorder characterized by a deficiency of the enzyme arginase, which is crucial in the final step of the urea cycle. This condition leads to the accumulation of arginine and other nitrogenous compounds in the blood, resulting in a variety of symptoms and complications.

Pathophysiology

Argininemia is caused by mutations in the ARG1 gene, which provides instructions for making the enzyme arginase. Arginase is responsible for converting arginine into ornithine and urea, a waste product excreted in urine. In individuals with argininemia, the lack of functional arginase leads to elevated levels of arginine in the blood, which can be toxic to the body.

Structure of Arginine

The accumulation of arginine and other byproducts can cause neurological symptoms, growth delays, and other systemic effects. The urea cycle is essential for removing excess nitrogen from the body, and its disruption can lead to hyperammonemia, a condition characterized by elevated levels of ammonia in the blood.

Clinical Features

Symptoms of argininemia typically appear in early childhood and may include:

• Developmental delay
• Spasticity
• Seizures
• Growth retardation
• Progressive neurological impairment

The severity of symptoms can vary widely among affected individuals. Some may experience mild symptoms, while others may have significant neurological and physical challenges.

Diagnosis

Diagnosis of argininemia is based on clinical evaluation, biochemical testing, and genetic analysis. Elevated levels of arginine in the blood and urine are indicative of the disorder. Genetic testing can confirm mutations in the ARG1 gene.

Treatment

Management of argininemia involves dietary restrictions and medications to reduce arginine levels and prevent complications. A low-protein diet supplemented with essential amino acids can help manage the condition. Medications such as sodium benzoate and sodium phenylbutyrate may be used to help remove excess nitrogen from the body.

Structure of Glycerol Phenylbutyrate

Glycerol phenylbutyrate is another medication that can be used to treat hyperammonemia by facilitating the excretion of nitrogen waste products.

Inheritance

Autosomal Recessive Inheritance Pattern

Argininemia is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected by the disorder. Carriers, who have only one copy of the mutated gene, typically do not show symptoms.

Prognosis

The prognosis for individuals with argininemia varies depending on the severity of the condition and the effectiveness of treatment. Early diagnosis and management can improve outcomes and quality of life. However, some individuals may experience significant neurological impairment despite treatment.

See also

• Urea cycle disorder
• Hyperammonemia
• Metabolic disorder
• Genetic disorder