These patients are likely to have a worse disease prognosis and poorer survival, its data show.
The study “Myopathy is a Risk Factor for Poor Prognosis of Patients with Systemic Sclerosis A retrospective cohort study” was published in the journal Medicine.
Muscle involvement is one of the most serious symptoms of scleroderma, or systemic sclerosis (SSc), with about one-third of all patients reporting muscle weakness. Of these people, 15% show muscle atrophy (shrinkage) and 10% have elevated blood levels of creatine kinase (CK), a biomarker of myopathy, or muscle disease.
While myopathy has been linked with a poorer prognosis (likely disease course) in people with scleroderma, few studies have investigated its associated clinical features.
Researchers in China analyzed clinical data covering 204 scleroderma patients (mean age of 52.8, 159 women and 45 men). All were followed between one and 48 months (four years), with an average follow-up time of 17.5 months.
Forty-four of these patients (21.6%) developed myopathy, and all of them had elevated CK levels. The majority of patients were diagnosed with myopathy based on an evaluation of their symptoms, but additional tests — such as electromyography, MRI scans and a biopsy — were also used.
The scientists observed that people with diffuse cutaneous systemic sclerosis (dcSSc) and shorter disease duration were more likely to develop myopathy than were those with limited cutaneous SSc (lcSSc). Twenty-six dcSSc patients had myopathy, as did 18 with lcSSc.
Patients with myopathy showed a significantly higher rate of interstitial lung disease (ILD) than did those without muscle involvement, 90% vs. 55.6%. Also more frequent were digestive problems (56.7% vs. 29.3%) and digital ulcers (41.2% vs. 25.6%) among the myopathy patient group.
In addition, these people had higher scores in the modified Rodnan Skin Score (mRSS), a measure of skin scarring, compared with those without myopathy (19.4 vs. 15.1). And a higher score on the Valentini score of disease activity was seen in myopathy patients (3.4) than in non-myopathy patients (2).
“SSc patients with myopathy have more severe skin involvement such as sclerosis and pigmentation changes,” the study noted.
No significant differences were seen in the frequency of arthritis or kidney involvement between the two groups.
A higher incidence of pulmonary hypertension (29.5% vs. 10.5%) and of fluid around the heart, or hydropericardium (25% vs. 10%) was also seen among patients with myopathy than in those without muscle disease. People with myopathy showed lower diffusing lung capacity for carbon monoxide, a measure of lung health that assesses how much oxygen travels from the lungs to the bloodstream.
Overall, these findings indicate more serious manifestations of scleroderma, affecting the cardiovascular and digestive systems, in patients with myopathy.
“[W]e found that the frequencies of ILD, PH, and cardiac involvement were significantly higher in SSc patients with myopathy. These manifestations lead to serious adverse consequence,” the researchers wrote.
As expected, myopathy patients had higher CK blood levels, 627.4 units/liter, than did those without myopathy, 59.3 units/liter.
Survival rates were poorer for those with muscle involvement than for other patients at three (97.7% vs. 98.8%), five (95.1% vs. 97.8%), and 10 years (81.4% vs. 94.1%).
“[O]ur results show that SSc patients with myopathy usually suffered from more severe clinical manifestations, such as cardiac, pulmonary, and esophageal involvement, particularly ILD and PH,” the researchers wrote.
“Myopathy was associated with higher disease activity, which affected the survival rate, leading to worse prognosis,” they added. “[E]arly screening for myopathy and timely aggressive intervention are crucial for improving a patients’ life quality and prognosis.”
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