Biallelic hypomorphic PGM3 mutations cause a rare autosomal recessive congenital disorder of glycosylation with a spectrum of clinical phenotypes, including T-B-NK + severe combined immunodeficiency with or without syndromic features, combined immunodeficiency, or primary atopic disorder (PAD) (1, 2, 3). The gene discussed is PGM3; the disease is immunodeficiency disease.