Supplementary Material for: Deranged Iron Status Evidenced by Iron Deficiency Characterizes Patients with Hidradenitis Suppurativa

Background: Proinflammatory activation and autoimmune processes underlie the pathophysiology of hidradenitis suppurativa (HS). Iron deficiency (ID) is frequently present in inflammation-mediated chronic diseases, irrespective of anemia. Objectives: We aimed to characterize iron status in patients with HS. Methods: Serum concentrations of ferritin, transferrin saturation (Tsat), soluble transferrin receptor and hepcidin were assessed as the biomarkers of iron status in 74 patients with HS and 44 healthy subjects. ID was defined as ferritin <100 µg/L or ferritin 100–299 µg/L with Tsat <20% (following the definition used in the other studies in chronic disease). Results: Compared with controls, patients with HS demonstrated a deranged iron status as evidenced by decreased levels of ferritin (91 ± 87 vs. 157 ± 99 µg/L), Tsat (21.5 ± 10.8 vs. 42.2 ± 11.7%) and hepcidin (31.3 ± 25.9 vs. 44.2 ± 22.0 ng/mL) (all p < 0.05 vs. controls). There was also a trend toward higher values of soluble transferrin receptor (1.23 ± 0.35 vs. 1.12 ± 0.19 mg/L) (p = 0.09 vs. controls). Disease severity (assessed with the Hidradenitis Suppurativa Severity Index and the 3-degree Hurley scale) did not differentiate iron status biomarkers. ID was present in 75% of HS patients, and its prevalence was not related with disease severity (Hurley I/II/III – 82 vs. 73 vs. 67%). In HS, none of the iron status biomarkers correlated with the levels of interleukin-6 (a marker of proinflammatory activation). Conclusions: The majority of HS patients demonstrate derangements in iron status typical of ID. These abnormalities are neither related to proinflammatory activation nor associated with disease severity. Whether it may have a therapeutic impact needs to be further studied.