Keywords: کمبود ایمنی ثانویه; Single ventricle; Fontan; Protein-losing enteropathy (PLE); T-cell lymphopenia; Hypogammaglobulinemia; Secondary immunodeficiency; Warts; ALC; absolute lymphocyte count; NK; natural killer; PLE; protein-losing enteropathy; SVSP; Single Ventricle Survivors