**1. Introduction**

Systemic sclerosis (Ssc) is a systemic autoimmune disease with incomplete known physiopathology. Its hallmark is represented by collagen deposition in various tissues that are accompanied by vascular injury [1]. As the clinical course of the disease can be severe in later Ssc stages, predictive biomarkers for severity and Ssc disease activity are necessary for better management of these patients [2]. Proteomic biomarkers are relatively easy to determine in the clinical laboratory setting using usual medical laboratory equipment. As such, there is an increased interest in research for proteomic biomarkers in Ssc patients. Previous mass spectrometry study pinpointed a relatively large number of candidate biomarkers for Ssc patients [3,4]. Nevertheless, the number of confirmed biomarkers on independent Ssc cohorts using specific assays (based on specific antibody-antigen reaction) is small. As such, studies are needed in order to confirm and evaluate the predictive value of candidate biomarkers on independent Ssc patient groups.

The study aimed to confirm circulating S100A6, calumenin, and cytohesin 2 as biomarkers for Ssc. These molecules were previously identified from various biologi-

**Citation:** Balanescu, P.; Balanescu, E.; Baicus, C.; Balanescu, A. S100A6, Calumenin and Cytohesin 2 as Biomarkers for Cutaneous Involvement in Systemic Sclerosis Patients: A Case Control Study. *J. Pers. Med.* **2021**, *11*, 368. https:// doi.org/10.3390/jpm11050368

Academic Editor: Mircea Tampa

Received: 11 April 2021 Accepted: 30 April 2021 Published: 2 May 2021

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cal Ssc samples as candidate biomarkers. To the best of our knowledge, this is the first confirmatory study for these molecules as circulatory biomarkers in Ssc patients.

## **2. Materials and Methods**

#### *2.1. Patient Evaluation*

Fifty-three consecutive Ssc patients that attended Colentina Clinical Hospital between January 2013 and January 2018 were included in the analysis (4 males and 49 females, median age 56 years). Patients were clinically evaluated and their cutaneous and visceral disease involvement was assessed.

Interstitial lung disease (ILD) was determined using X-ray imaging and high resolution CT. Flow spirometry and diffusing capacity for carbon monoxide-DLCO was determined in these patients (QUARK PFT station, Cosmed, Rome, Italy).

Pulmonary hypertension was indirectly determined by transthoracic echocardiography (Hitachi Aloka SSD 4000 ultrasound machine, Hitachi, Japan). Possible pulmonary hypertension was considered when the patients had at least 35 mm Hg at rest in pulmonary artery [5]. Cardiac involvement was determined using cardiac ultrasonography and EKG (Cardiocontrol, MDIMedical, Belfast, UK).

Frequency of Raynaud was interpreted as daily or less frequent. Presence of telangiectasias, ischemic digital ulcers, and calcinosis were recorded as previously defined in the literature [6]. Severity of skin involvement was evaluated using modified Rodnan skin score [7].

Disease activity score was evaluated with EUSTAR criteria [8]. Gastrointestinal involvement was evaluated using upper gastrointestinal endoscopy and radiographic examinations including barium swallow for esophageal motility. Inflammatory markers were also recorded in Ssc patients (erythrocyte sedimentation rate (ESR) and serum C reactive protein (CRP) concentration). Patient medication at the time of enrollment was also recorded.

Twenty-six age- and gender-matched controls were recruited in this study (2 males, 24 females, median age 51.5 years) from patients referred to Colentina Clinical Hospital. Controls had no previous record of Raynaud's phenomenon and no active inflammation.

Patients and controls signed the informed consent. The study was conducted according to the Declaration of Helsinki and was approved by the local ethics committee (decision No. 10/11 September 2020).
