**4.5 Cardiac involvement**

Cardiac involvement in SSc can be seen in two ways: primary and secondary. Secondary involvement may be secondary to pulmonary arterial hypertension, interstitial lung disease, or kidney disease [33]. Primarily, all layers of the heart, conduction system, coronary vessels, and valves can be involved. Because of these involvements, pericardial effusion, supraventricular or ventricular arrhythmias, conduction disorders, valve regurgitation, myocardial ischemia, myocardial hypertrophy, and heart failure may develop [34].

Because myocardial findings are often faint, especially in the early stage, it is very difficult to detect these patients. However, when the involvement progresses to the symptomatic stage, the patient develops one of the poor prognostic factors [31]. Therefore, early diagnosis of cardiac involvement in SSc is very important. Electrocardiography or echocardiography is not effective in detecting cardiac fibrosis. Magnetic resonance imaging (MRI) is the only method that can detect cardiac involvement in the early stages of the disease. A cardiac MRI can show myocardial inflammation, fibrosis, decreased perfusion of the heart muscle, and ventricular dysfunction [35].

#### **4.6 Renal involvement**

Renal involvement in scleroderma is quite common. Even though it appears often as mild renal dysfunction, it can also cause a severe clinical table called scleroderma renal crisis (SRC). The pathogenesis of SRC is not fully known, but studies suggest vasculopathy as a source. Corticosteroids and vasospasm-causing drugs (tacrolimus, cyclosporine, and cocaine) may play a role in the etiology [36]. The risk of SRC development increases in the presence of the autoantibodies anti-RNA polymerase III, anti-topoisomerase I, and anti-U3RNP [36].

Some patients show a chronic clinical table with gradual decrease in eGFR, increase in serum creatinine concentration, proteinuria, hematuria, and moderate arterial hypertension [31].

Decreased glomerular filtration rate, increased serum creatinine, hemolytic anemia, proteinuria, and decreased platelet count are laboratory findings indicating renal involvement [31].
