Among proteins represented by peptides increased in patients with HF, several proteins present in blood were found, including beta‐2‐microglobulin (a component of the major histocompatibility antigen indicating activation of the immune system and widely considered to reflect renal tubular function), 35 kDa inter‐alpha‐trypsin inhibitor heavy chain H4 (an acute‐phase protein participating in inflammatory responses to trauma), apolipoprotein C‐III (involved in triglyceride homeostasis), and matrix Gla protein (an inhibitor of vascular mineralization involved in bone organization). The gene discussed is APOC3; the disease is hydrops fetalis.