Decrease in Hemoglobin Levels during Acute Attacks in Patients with Idiopathic Recurrent Pericarditis: A Model of Anemia in Acute Disease

<b>Background/Objectives:</b> Anemia during acute inflammation is not well described in the literature. We aimed to study whether patients develop a transient hemoglobin decrease during an acute attack of recurrent pericarditis. <b>Methods:</b> We retrospectively analyzed patients with recurrent pericarditis. The primary endpoint was the difference in hemoglobin levels during an acute attack and in the following remission. As secondary endpoints, we correlated this variation with laboratory and clinical features; we also evaluated the available baseline hemoglobin values. <b>Results:</b> Sixty-two patients, including thirty females (48.4%), with a median age of 39 years, were observed during an acute attack and remission. The attack indexed was the first in 21 patients and the second or the third in 41, with pre-attack hemoglobin levels available for the latter group. Median hemoglobin levels (IQR) were 13.8 (12.8-15.1) g/dL at baseline, 12.0 (11.2-13.4) during attacks and 13.6 (13.1-14.0) during remission (<i>p</i> < 0.001). The median hemoglobin reduction between an acute attack and remission was 1.4 g/dL. Their mean corpuscular volume remained in the normal range. Hb reduction significantly correlated with C-reactive protein (CRP) elevation, neutrophilia and the neutrophil-to-lymphocyte ratio, but not serosal involvement. Only CRP elevation remained associated with the variation of Hb in a multivariate analysis (<i>p</i> = 0.007). <b>Conclusions:</b> This study is a proof of concept: hemoglobin levels may decline rapidly during acute inflammation in correlation with CRP elevation, with transient normocytic anemia, followed by a rapid rebound. In this regard, idiopathic pericarditis may represent a pathogenetic model of this type of anemia.