PLN and hydrops fetalis: Studies on patients with HF have reported reduced SERCA2a and PLN transcript levels, but findings at the protein level have been less consistent.1,2 The prior studies have been limited by small numbers of patients with heterogeneous causes of HF.1,2 Despite promising results in animal models, clinical trials of gene therapy for SERCA2a overexpression have not yet shown significant improvement in outcomes.3 Therefore, our aim was to conduct a comprehensive investigation of the protein levels of SERCA2a and PLN in patients with HF.