FNIP1 and agammaglobulinemia: FNIP1 LOF in humans is associated with immunodeficiency characterized by hypogammaglobulinemia, neutropenia, and recurrent infections along with cardiac involvement, including hypertrophic cardiomyopathy (HCM), tachyarrhythmias, and pre-excitation syndromes (Niehues et al. 2020; Saettini et al. 2021).