Aldolase: A Myositis Biomarker
The month of May is devoted to myositis awareness, a muscle-wasting disease resulting in reduced muscle strength and fatigue. The term ‘myositis’ is an umbrella term referring to the “general inflammation or swelling of the muscle”. However, myositis is more often referred to as a disease involving chronic inflammation of the muscles which does not improve with rest. This condition is also known as idiopathic inflammatory myopathy (IIM) 1.
Myositis is an autoimmune disease characterised by pain, muscle weaknesses, swelling and extreme fatigue which often gradually appear. Myositis can be potentially life-threatening, especially dermatomyositis which affects the heart muscle and lungs. Whilst a rare disease, it is estimated that 75,000 Americans suffer from myositis, however, many are undiagnosed or misdiagnosed with more common autoimmune diseases. Most physicians are unfamiliar with the disease and symptoms and so the consequences of this can be catastrophic in terms of long-term physical muscle damage, disability and even death 1, 2, 3.
Table 1 reviews the different forms of myositis
Table 2 reviews complications with or due to myositis
It is vital that physicians are educated to include myositis despite it being a rare disease as it is essential that myositis patients are diagnosed quickly to ensure appropriate treatment plans are implemented.
Aldolase Testing
Aldolase testing has been recognised as a marker in the differential diagnosis of muscle weakness as aldolase levels remain consistent where weakness is caused by neurological problems such as multiple sclerosis (MS). Aldolase is an enzyme specifically found in skeletal muscle and the liver. When either the muscle or liver are damaged, aldolase is released into the bloodstream 13 . A few studies support aldolase testing in the diagnosis of myositis:
1. Arthritis Research & Therapy (2012): Aldolase predicts subsequent myopathy occurrence in systemic sclerosis 14
Objective:
A French monocentric 4-year study prospectively evaluated n=137 systemic sclerosis (SSc) patients without proximal muscle weakness to assess the risk of myopathy related systemic sclerosis (Myo-SSc) according to the European Neuro Muscular Centre criteria. Aldolase, creatine kinase (CK), C-reactive protein (CRP), alanine transaminase (ALT) and aspartate transaminase (AST) were evaluated.
Conclusion:
Aldolase is a valuable diagnostic tool in the identification of SSc patients at a high risk of developing subsequent Myo-SSc. This enables clinicians to monitor at-risk patients as well as identifying Myo-SSc in its earliest stages, enabling the effective and swift implementation of an appropriate treatment plan when the muscle damage is still in a reversible stage.
Findings:
2. Clinical and Experimental Rheumatology (2013): Isolated elevation of aldolase in the serum of myositis patients: a potential biomarker of damaged early regenerating muscle cells 15
Objective:
The in vitro analysis of the gene and protein expression levels of aldolase and CK during muscle cell differentiation.
Conclusion:
Aldolase A is expressed in the absence of CK in undifferentiated muscle cells and in the early differentiation process. Isolated elevated serum aldolase A in myositis patients reflects preferential immune-mediated damage of early regenerative cells. Aldolase is a biomarker of damaged early regenerating muscle cells.
Findings:
Myositis can be a potentially life-threatening disease when undiagnosed or misdiagnosed. Aldolase is recognised as a biomarker in the diagnosis and monitoring of myositis. Randox are one of the only in-vitro diagnostic manufacturers to offer the aldolase assay in an automated and manual biochemistry format. Not only does the Randox methodology have an excellent correlation coefficient to r=0.9917 when compared against standard methods, the Randox assay is lyophilised for enhanced stability with an excellent measuring range of 1.73 – 106U/l. Moreover, applications are available detailing instrument-specific settings for the convenient use of the Randox aldolase assay on a wide range of clinical chemistry analysers.
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References
[1] The Myositis Association. About Myositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/.
[2] Kobert, Linda. Myositis, a rare muscular inflammatory disease that ofen goes undiagnosed or misdiagnosed, disproportionally impacts women of color. s.l. : The Myositis Organisation.
[3] Muscular Dystophy UK. Myositis. [Online] [Cited: May 6, 2019.] https://www.musculardystrophyuk.org/about-muscle-wasting-conditions/myositis/.
[4] The Myositis Association. Types of Myositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/.
[5] —. Sporadic Inclusion Body Myositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/sporadic-inclusion-body-myositis/.
[6] —. Dermatomyositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/dermatomyositis/.
[7] —. Polymyositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/polymyositis/.
[8] —. Necrotizing Myopathy. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/necrotizing-myopathy/.
[9] —. Juvenile Myositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/types-of-myositis/juvenile-myositis/.
[10] —. Cancer-associated myositis. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/complications/cancer-associated-myositis/.
[11] —. Infection. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/complications/infection/.
[12] —. Cardiovascular Disease. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/complications/cardiovascular-disease/.
[13] —. Blood Tests. [Online] [Cited: May 3, 2019.] https://www.myositis.org/about-myositis/diagnosis/blood-tests/.
[14] Aldolase predicts subsequent myopathy occurrrence in systemic sclerosis. Tolédano, Cécile, et al. Faubourg Saint-Antoine : Arthritis Research & Therapy, 2012.
[15] Isolated elevation of aldolase in the serum of myositis patients: a potential biomarker of damaged early regenerating muscle cells. Casciola-Rosen, Livia, et al. Baltimore : Clinical and Experimental Rheumatology, 2013.