In particular, patient 1 carried two heterozygous ADA variants (c.58G>A, p.Gly20Arg and c.956_960del, p.Glu319Glyfs); patient 2 harbored two discrete pathogenic variants in the DCLRE1C gene (a large deletion of exons 1–3 and the nonsense mutation c.241C>T, p.Arg81*), causing Artemis deficiency; and patient 3 carried a hemizygous IL2RG missense variant (c.437T>C, p.Leu146Pro), associated with X-linked SCID. The gene discussed is ADA; the disease is severe combined immunodeficiency due to DCLRE1C deficiency.