In line with previous studies20,34, FGF23 also correlated with NYHA and Killip classification status as clinical indicators of HF severity, albeit with the important caveat that most patients in our study had no or mild limitations of physical activity before admission (i.e., 65.4% of patients were NYHA I or II), and the vast majority (88.7% of patients) had no overt pulmonary edema (Killip class III) or signs of cardiogenic shock (Killip class IV) at admission. The gene discussed is FGF23; the disease is hydrops fetalis.