Elevated baseline serum creatine kinase in Thai early systemic sclerosis patients is associated with high incidence of cardiopulmonary complications and poor survival: an inception cohort study.

Background: Inception cohort data regarding the incidence of cardiopulmonary complications in early systemic sclerosis (SSc) patients comparing those with and without elevated baseline creatine kinase (CK) are limited. This study aimed to compare the incidence of cardiopulmonary complications and survival between the two subgroups.

Methods: We used an inception cohort study of early SSc patients seen at the Rheumatology Clinic, Maharaj Nakorn Chiang Mai Hospital, Thailand, from January 2010 to December 2019. All patients were assessed for clinical manifestations and CK levels and underwent echocardiography and HRCT at the study entry and annually thereafter.

Results: A total of 144 SSc patients (84 female, 115 diffuse cutaneous SSc (DcSSc)) with a mean disease duration of 11.9 ± 9.2 months were enrolled. At cohort entry, their mean ± SD CK levels were 364.3 ± 598.0 U/L. The participants were then divided into two subgroups: (i) 29 SSc with elevated CK (baseline CK ≥ 500 U/L); (ii) 115 SSc with non-elevated CK. At enrollment, the elevated CK group was characterized by a higher proportion of male gender, DcSSc subtype, arthritis, and weakness; shorter disease duration; and higher MRSS compared with non-elevated CK. At the last visit, with a mean ± SD follow-up duration of 6.2 ± 2.7 years, the elevated CK group showed a higher cumulative prevalence of weakness, dysphagia, LVEF < 50%, and suspected myocardial disease; higher incidence of LVEF < 50%, suspected myocardial disease, and ILD; and shorter survival time.

Conclusion: It was found in our study cohort that elevated baseline serum CK in early SSc, of which majority were DcSSc subtype, is associated with more severe clinical presentation, higher incidence of cardiopulmonary complications, and shorter survival time compared with the non-elevated CK subgroup. Key Points • In early SSc patients, elevated baseline serum creatine kinase was confirmed to be associated with a high incidence of cardiac and ILD complications, and poor long-term survival time. • Careful evaluation of baseline serum CK levels in all early-diagnosed SSc patients is crucial in general clinical practice.