Prevalence, causes, and clinical associations of anemia in patients with systemic sclerosis: A cohort study

Background: Anemia is considered a risk factor of severity in systemic sclerosis. Yet, limited data are available on the frequency and causes of anemia in systemic sclerosis. The objectives of our study were to determine the frequency and causes of anemia in systemic sclerosis, to analyze the clinical and biological characteristics of patients with anemia, and to assess the association between anemia and systemic sclerosis prognosis. Methods: We conducted a prospective single-center study from January 2017 to May 2022. Patients underwent a hemoglobin assay and a standardized etiological workup to determine the causes of anemia at the initial visit. Clinical and biological parameters were compared between patients with anemia and those with normal hemoglobin levels. We followed up patients until May 2023 and compared their survival. Results: A total of 502 systemic sclerosis patients, including 107 diffuse cutaneous systemic sclerosis, were included. At enrollment, 100 patients had anemia. The primary cause of anemia was iron deficiency (40%). Among the 32 patients with iron deficiency-associated anemia who underwent gastrointestinal exploration, 56% had digestive bleeding, with upper gastrointestinal tract involvement being the main cause (90%). Patients with anemia at enrollment had higher systemic sclerosis severity scores and more gastrointestinal symptoms compared to patients without anemia (p < 0.05). They exhibited higher systolic pulmonary artery pressure, lower anemia-corrected diffusing capacity for carbon monoxide, and lower forced vital capacity (p < 0.05). During follow-up, 65 patients (14.8%) died. After adjusting for age, systemic sclerosis subtypes, forced vital capacity, and pulmonary arterial hypertension, anemia at inclusion was associated with a higher mortality rate (hazard ratio: 1.94 (95% confidence interval: 1.39-2.48), p = 0.02). Conclusion: Our study shows a high frequency of anemia among patients with systemic sclerosis. Most anemias are due to iron deficiency, and gastrointestinal exploration can identify bleeding in the majority of the cases. In addition, our study confirms that systemic sclerosis patients with anemia have a more severe disease and a higher mortality rate.