NeurometPlus

Incidence

It is the least common of the UCD. AR inheritance. Apparently never seen in Saudi Arabia. Arginase deficiency is caused by mutations in the ARG1 gene and is inherited in an autosomal recessive manner.

Clinical Characteristics

Arginase deficiency is an inherited metabolic disease in which the body is unable to process arginine (a building block of protein). It belongs to a group of disorders known as urea cycle disorders. These occur when the body\'s process for removing ammonia is disrupted, which can cause ammonia levels in the blood to rise (hyperammonemia). In most cases, symptoms appear between the ages of one and three years. Most people with arginase deficiency appear to be healthy at birth and have normal development during early childhood. The first features of arginase deficiency often appear between the ages of one and three years. In some cases, symptoms may begin earlier or later. Symptoms may include feeding problems, vomiting, poor growth, seizures, and stiff muscles with increased reflexes (spasticity). People with arginase deficiency may also have developmental delay, loss of developmental milestones, and intellectual disability, stiff muscles and increased reflexes (spasticity). Signs and symptoms may include: Poor growth (present in all the people who have arginase deficiency), also developmental delay, loss of previously acquired developmental milestones, intellectual disability, seizures, small head size (microcephaly), problems with balance and coordination.
Occasionally, people with arginase deficiency have episodes of severe hyperammonemia. Although rare, these episodes are more likely to occur following a high-protein meal or during periods of stress caused by illness or fasting. Hyperammonemia can cause irritability, lethargy, refusal to eat, breathing difficulty, movement disorders, vomiting and, in severe cases, coma.
This condition is characterized by early progressive spastic tetraplegia, worse in lower extremities, associated with loss of mental skills. Behaves as a CP case. Seizures, ataxia and athetosis can be additional signs. Symptoms of chronic hyperammonemia. Rarely acute crisis of metabolic decompensation are noted. There may be irritablity and inconsolable crying. If arginase deficiency is undiagnosed or if the person with the disorder is unable to follow the strict low-protein diet, severe intellectual disability and muscle stiffness may develop, as well as loss of the ability to walk and loss of bladder and bowel control.
Treatment is focused on lowering arginine levels and preventing hyperammonemia. People with arginase deficiency are generally placed on a very low-protein diet with the help of a registered metabolic dietitian. They may be prescribed certain medications called nitrogen-scavenging drugs.

Precipitants

none. Protein ingestion make symptoms worse.

Provocation Tests

no

Diagnostic Procedures

EB liver & red cells. Also F and WBC. A diagnosis of arginase deficiency is often suspected based on the person\'s signs and symptoms. Special blood tests to measure levels of arginine and ammonia may then be ordered. A diagnosis of arginase deficiency is confirmed when genetic testing identifies a disease-causing mutation in each copy of the ARG1 gene or a blood test demonstrates reduced arginase enzyme activity in the red blood cells.