The concentration of galectin-3 in serum of patients with AF and MS is higher than in patients with MS without AF (10.3 (4.8–15.4) and 5.1 (4.3–8.8) ng/mL, p < 0.0001) and higher than in healthy subjects (10.3 (4.8–15.4) and 3.2 (2.4–4.2) ng/mL, p < 0.0001). The gene discussed is LGALS3; the disease is myeloid sarcoma.