Decoding the Mystery: Understanding Hereditary Neuralgic Amyotrophy (HNA)

Expert Reviewed By: ⁠Dr. Brandon Colby MD

Hereditary Neuralgic Amyotrophy (HNA) is a rare genetic disorder that affects the peripheral nerves, causing pain, muscle weakness, and sometimes even paralysis. This article aims to provide a comprehensive understanding of HNA, its diagnosis, and the role of genetic testing in managing this complex condition.

What is Hereditary Neuralgic Amyotrophy (HNA)?

HNA is a genetic disorder that primarily affects the brachial plexus, a network of nerves controlling the muscles of the shoulder, arm, and hand. The condition is characterized by recurrent episodes of severe pain and muscle weakness, often triggered by external factors such as injury, stress, or infection (1). HNA is inherited in an autosomal dominant manner, meaning that an affected individual has a 50% chance of passing the condition to their offspring.

Diagnosing HNA

Diagnosing HNA can be challenging due to its variable presentation and rarity. A thorough clinical evaluation, including a detailed family history and physical examination, is essential in identifying the condition. Electrophysiological studies, such as nerve conduction studies and electromyography, can provide valuable information on nerve function and help rule out other potential causes of the symptoms (3).

Genetic Testing for HNA

Genetic testing plays a crucial role in confirming the diagnosis of HNA and understanding the underlying genetic cause. The condition has been linked to mutations in the SEPT9 gene, located on chromosome 17 (2). Genetic testing can detect these mutations and provide a definitive diagnosis.

Benefits of Genetic Testing for HNA

Genetic testing for HNA offers several benefits, including:

• Confirming the diagnosis: A positive genetic test result can provide a definitive diagnosis of HNA, allowing for appropriate management and treatment strategies to be implemented.
• Identifying at-risk family members: Genetic testing can identify unaffected family members who carry the HNA-causing mutation, allowing for early intervention and monitoring of potential symptoms.
• Guiding reproductive decisions: Couples with a family history of HNA can utilize genetic testing to understand their risk of having an affected child and make informed decisions about family planning.
• Furthering research: Identifying the genetic basis of HNA can help researchers better understand the condition and develop targeted therapies in the future.

Limitations of Genetic Testing for HNA

While genetic testing offers significant benefits, it is essential to be aware of its limitations, such as:

• Genetic heterogeneity: Not all cases of HNA are caused by mutations in the SEPT9 gene, and some individuals may have a genetic cause that has not yet been identified (4). In such cases, genetic testing may not provide a definitive diagnosis.
• Variable expressivity: The severity and presentation of HNA can vary widely, even among family members with the same genetic mutation. A positive genetic test result does not necessarily predict the severity or course of the condition.
• Psychosocial considerations: Receiving a positive genetic test result for HNA can have significant emotional and psychological implications for both the individual and their family members. It is essential to provide appropriate counseling and support throughout the testing process.

Conclusion

Hereditary Neuralgic Amyotrophy (HNA) is a complex genetic disorder that requires a thorough understanding of its clinical presentation, diagnostic methods, and the role of genetic testing in managing the condition. Genetic testing can provide valuable information for affected individuals and their families, guiding treatment decisions and identifying at-risk family members. However, it is crucial to consider the limitations of genetic testing and provide appropriate support and counseling throughout the process.

About The Expert Reviewer

Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of  and the author of ⁠⁠Outsmart Your Genes.

Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (⁠⁠ACMG), an Associate of the American College of Preventive Medicine (⁠⁠ACPM), and a member of the National Society of Genetic Counselors (⁠NSGC)