In 2012, Abdollahpour et al. reported a homozygous premature termination mutation of MST1 with a novel clinical phenotype including T- and B-cell lymphopenia, intermittent neutropenia, and atrial septal defects; this suggest that MST1 deficiency is a novel human primary immunodeficiency syndrome. The gene discussed is MST1; the disease is Abnormal cardiac septum morphology.