ADA2 and hyperinsulinemic hypoglycemia, familial, 4: In 2014, biallelic deleterious mutations in the cat eye chromosome region 1 gene (CECR1, subsequently renamed ADA2), encoding adenosine deaminase 2 (ADA2), were reported as the cause of a monogenic inborn error of immunity disease, deficiency of ADA2 (DADA2) (OMIM # 615,688) [1, 2].