Researchers at Sun Yat-sen University, China recently published in the journal Disease Markers a new method to help assess muscular dystrophy disease severity and progression. The study is entitled “Serum Creatinine Level: A Supplemental Index to Distinguish Duchenne Muscular Dystrophy from Becker Muscular Dystrophy.”
Muscular dystrophies are characterized by a progressive skeletal muscle weakness that leads to the degeneration of muscle cells and tissues, compromising locomotion. It can also affect specific muscles involved in respiratory function, leading to breathing complications and cardiac problems. Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are two muscular dystrophies caused by mutations in the dystrophin gene. DMD has a rapid progression and a phenotype more severe than BMD, where the majority of the patients requires a wheelchair by the age of 12 and often succumb to the disease in their 20s. BMD has a milder phenotype with near-normal life expectancy. Both disorders affect mainly boys.
Several therapeutic strategies aiming at restoring dystrophin production are currently undergoing clinical testing, although reliable and convenient measures to assess disease severity and progression are urgently needed. Many of the tools available such as immunohistochemistry or quantitative muscle strength tests are not considered feasible or adequate for monitoring the patient’s response to therapy due to the invasiveness of the procedure (in the case of muscle biopsy), or due to their subjectivity and difficulty to conduct in young children.
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Creatinine is an end product generated during muscle metabolism and its excretion has been reported to progressively decrease in parallel with muscle wasting in DMS patients, suggesting that a 24-hour urinary creatinine excretion test could be a reliable indicator of muscle mass. Since serum creatinine levels strongly correlate with urinary creatinine excretion levels and DMS patients usually have lower creatinine serum levels in comparison with BMD patients, the research team hypothesized that serum creatinine levels could represent a useful marker to determine disease severity.
Researchers analyzed a cohort of 212 Chinese boys with muscular dystrophies in terms of clinical, biochemical, genetic and motor parameters to evaluate whether serum creatinine levels could reflect disease severity. The research team found that serum creatinine levels had a moderate to strong inverse correlation with lower extremity motor function, suggesting that patients with lower creatinine levels may have a more severe disorder with greater impairment of the motor function. It was also found that creatinine levels were significantly higher in BMD patients in comparison to DMD patients, indicating that a higher serum creatinine level is linked to a milder disease.
The researchers concluded that serum creatinine levels reflect disease severity and could potentially be used as a simple biomarker to clinically discriminate between DMD and BMD patients and help assess disease progression.