E72.22 Arginosuccinic aciduria

Name of the Condition

• Arginosuccinic aciduria (ICD-10 Code: E72.22)

Summary

Arginosuccinic aciduria is a rare genetic disorder affecting the urea cycle, where the body cannot properly remove ammonia from the blood. This results in elevated levels of ammonia, which is toxic and can lead to severe health issues. The condition is caused by a deficiency in the enzyme argininosuccinate lyase, which is essential for converting argininosuccinic acid into arginine and fumarate in the urea cycle.

Causes

Arginosuccinic aciduria is caused by mutations in the ASL gene, which encodes the enzyme argininosuccinate lyase. It is inherited in an autosomal recessive pattern, meaning an individual must inherit two mutated copies of the gene (one from each parent) to develop the condition. These mutations disrupt the normal breakdown of argininosuccinic acid, leading to its accumulation and impaired ammonia detoxification.

Risk Factors

• Family history of arginosuccinic aciduria or other urea cycle disorders.
• Consanguinity (parents who are close relatives) increasing the likelihood of inheriting recessive mutations.
• Ethnic or geographic prevalence of specific ASL gene variants in certain populations.

Symptoms

• Neurological symptoms such as lethargy, seizures, developmental delays, or intellectual disability.
• Gastrointestinal issues like vomiting, poor feeding, or failure to thrive.
• Hepatomegaly (enlarged liver) or liver dysfunction.
• Abnormal hair growth (trichorrhexis nodosa) in some cases.

Diagnosis

Diagnosis typically involves newborn screening, blood tests showing elevated ammonia and argininosuccinic acid levels, and genetic testing to confirm mutations in the ASL gene. Urine organic acid analysis may also reveal increased argininosuccinic acid excretion.

Treatment Options

• Low-protein diet with essential amino acid supplements to limit ammonia production.
• Medications such as sodium benzoate or arginine to help remove ammonia and support urea cycle function.
• In severe cases, liver transplantation may be considered as a treatment option.

Prognosis and Follow-Up

Prognosis depends on the severity of the condition and the timeliness of treatment. Early diagnosis and strict adherence to dietary and medical management can improve outcomes. Regular monitoring of ammonia levels, nutritional status, and neurological development is essential for long-term follow-up.

Complications

• Severe hyperammonemia leading to coma or brain damage.
• Developmental delays or intellectual disability if untreated.
• Liver dysfunction or failure in advanced cases.
• Recurrent episodes of metabolic crisis due to protein intake or illness.

Lifestyle & Prevention

• Strict adherence to a low-protein diet and prescribed supplements.
• Avoidance of triggers like prolonged fasting or illness, which can increase ammonia production.
• Regular medical follow-up to adjust treatment plans as needed.

When to Seek Professional Help

Seek immediate medical attention if symptoms such as lethargy, seizures, vomiting, or altered mental status occur, as these may indicate hyperammonemia requiring urgent intervention.

Tips for Medical Coders

When coding for arginosuccinic aciduria (E72.22), ensure documentation supports the diagnosis, including genetic testing results or biochemical evidence of elevated argininosuccinic acid. Verify that the code is used for confirmed cases and not for unspecified urea cycle disorders. Document any associated complications or treatment plans to support accurate coding.