Myopathies Linked to Worse Outcomes in Systemic Sclerosis

Patients with systemic sclerosis (SSc) as well as myopathy had more severe clinical manifestations and worse disease activity than those without, which in turn impacted survival rates and prognosis, according to a recent study.

SSc, a connective tissue disease, is marked by fibrosis and microvascular injury to the skin and internal organs. Many patients have multiple system involvement, including the respiratory system, digestive system, skin, joints, and kidneys.

Pulmonary issues are the main cause of mortality; cumulative survival from diagnosis has been estimated at 74.9% at 5 years and 62.5% at 10 years. 

About one-third patients complain of myopathy, or muscle weakness. About 15% of those have objective muscle atrophy and 10% have elevated serum creatine kinase (CK), according to the authors of the study. The frequency of myopathy in SSc ranges from approximately 10% to 15% when systematically assessed, and muscle weakness occurs in as many as 90% of these patients, said the researchers, who sought to compare clinical characteristics and identify long-term outcomes of patients with and without muscle involvement.

The impetus for the study, they said, was their belief that SSc-associated myopathy does not get enough attention in either clinical or research settings. The researchers retrospectively investigated the medical records, laboratory results, and computed tomography images of 204 consecutive patients with SSc in China. 

At diagnosis, these patients had symptoms of muscle involvement such as fatigue, muscle weakness, muscle pain, and at least 1 of these conditions: serum CK over the normal value (145 U/L); inflammatory changes documented by muscle biopsy (including necrosis, acute neurogenic atrophy, and fibrosis); EMG changes of low voltage, short duration potential during maximal contraction, fibrillation, or sharp waves. In addition, patients with myopathy had muscle MRIs showing edema, atrophy, and hyperemia.

Results showed that the prevalence of myopathy was 21.6%, higher than other previously reported studies. Results also showed that patients with myopathy were more likely to develop:

Diffuse cutaneous involvement (90.9% vs 56%; P = .006)

Interstitial lung disease (90% vs 56%; P < .001)

Digestive system involvement (56.7% vs 29.3%; P = .001)

Pulmonary hypertension (29.5% vs 10.5%; P = .004)

Pericardial effusion (25% vs. 10%; P = .019)


Patients with myopathy had lower single-breath diffusing capacity of the lung for carbon oxide (46.5 [11.1] vs 57.1 [13.4]; P  < .001).

The researchers found that interstitial lung disease, pulmonary hypertension, and cardiac involvement were also significantly higher in patients with SSc who also had myopathy. In addition, the Kaplan–Meier survival analysis showed that patients with myopathy had decreased overall survival compared with patients without myopathy ( P = .028).

Reference

Zhou M, Jiang L, Nie L, et al. Myopathy is a risk factor for poor prognosis of patients with systemic sclerosis: A retrospective cohort study. Medicine (Baltimore). Published online August 14, 2020. doi: 10.1097/MD.0000000000021734