Genetics of Shoulder Impingement Explained

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How is "Shoulder Impingement" encoded by the genome?

‍‍Shoulder impingement syndrome (SIS) is a common shoulder disorder, accounting for an estimated 44–65% of all shoulder complaints. It occurs when the acromion (the top outer edge of the shoulder) pinches or rubs against the rotator cuff, which is positioned directly below. The symptoms include pain at the top and outer side of your shoulder, and pain increases when you lift your arm overhead. 

Athletes and others who perform an excessive amount of overhead rotational motion are more susceptible to shoulder impingement syndrome. But could SIS also have a genetic component? 

Is Shoulder Impingement Inherited?

The chances of getting a rotator cuff injury increase as you age and are more common among people who perform repetitive overhead motions, such as carpenters or painters. However, injuries like shoulder impingement do appear to be more common in some families. 

One study led by researcher Ostlere Harvie found that rotator cuff tears were more common among siblings than among spouses. 

Another study determined that a higher rate of shoulder injuries only occurs among closely related family members. When distant relatives were studied, heritability indicators decreased. This suggests that environmental factors must also play a role. 

A common problem recognized with studies on rotator cuff disease is the assumption that shoulder injuries are naturally low in the general population. That assumption may be incorrect. People with only minor shoulder impingement pain may not seek medical care. 

‍Which Genes Are Connected to Shoulder Impingement Syndrome?

Several pathogenic factors have been associated with SIS, including acromial morphology (the shape and structure of the shoulder joint), muscular imbalance, capsular laxity or tightness (irregular tenseness in the shoulder ligaments), rotator cuff muscle weakness, cuff muscle weakness, and degeneration and inflammation of the tendons or bursa. 

Despite the prevalence, the mechanisms from a molecular and genetic level for SIS are still unclear. A genome-wide association study (GWAS) was recently performed to identify the genetic variants associated with neck or shoulder pain in the UK Biobank cohort, and three genetic loci were identified. Here, researchers performed another GWAS and further conducted a gene set enrichment analysis to detect the candidate genes and pathways associated with developing SIS.

‍For this GWAS, researchers used genetic samples that included 3,626 cases diagnosed with SIS according to the International Classification of Diseases 10 (ICD-10), and 3,626 matched controls. Two SNPs showed significant relationships after controlling for variables such as age and sex. 

In addition, several candidate loci with suggestive association signals were identified, which include the following SNPs: rs2130118 of the Annexin A1 (ANXA1) gene on chromosome 9, rs7322063 on chromosome 13, rs9302983 on chromosome 17, rs6984411 on chromosome 8, and rs789644 of the SIPA1L2 gene on chromosome 1. The ANXA1 gene encodes a membrane-localized protein that aids in anti-inflammatory activity. Further, the gene enrichment analysis researchers performed identified some candidate pathways which are linked to infection response and oxygen levels in tissues.‍

Although this is the first molecular mechanism study of SIS combining GWAS and a gene set enrichment analysis, the researchers addressed several limitations in the study. First, the sample size of this SIS GWAS is not large enough. Additionally, the findings need to be verified via more experimentation, thus results are interesting but certainly not conclusive. 

Further studies are needed to confirm the findings and reveal the potential roles of identified loci and pathways in the development of SIS. Read more about the study here: https://pubmed.ncbi.nlm.nih.gov/32690583/

‍Did You Inherit Shoulder Impingement Syndrome?

Like many health issues, shoulder impingement syndrome may have a genetic connection. Carrying the gene variant for SIS doesn’t mean you are destined to develop the problem, but it could mean you are at a higher risk. 

Knowing your genetic predisposition to SIS can help you lower the risks and improve your chances of staying healthy. 

Insight into your genetic code provides the knowledge needed to adjust your diet, exercise, and lifestyle habits in ways that are specifically focused on your unique needs. You can’t change your DNA, but you can target self-care to strengthen deficits and minimize health risks. 

A better understanding of the genetic component involved with SIS could lead to the development of more effective treatments and prevention protocols for those susceptible to the problem. 

Taking a DNA test to learn more about your ancestry is fun and informative, but don’t stop there. Uploading your raw DNA data to Genomelink provides an amazing amount of information you can use to make your life better. 

Are you interested in learning more about your genetic tendency for shoulder impingement syndrome? Upload your DNA results to Genomelink today, then login to your Genomelink YOUR TRAITS to see this new genetic trait.

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