Niehues et al. (2020) described 3 patients with homozygous FNIP1 variants causing hypogammaglobulinemia, recurrent sinopulmonary and gastrointestinal infections, cardiac involvement with HCM, Wolff-Parkinson-White (WPW) syndrome, and metabolic myopathy in a single patient. The gene discussed is FNIP1; the disease is agammaglobulinemia.