Table 1.

Classification of PID according to IUIS Primary Immunodeficiency Diseases Committee Report on Inborn Errors of Immunity (1, 2).

I. Immunodeficiencies affecting cellular and humoral immunity
a. Severe Combined Immunodeficiency (SCID) defined by CD3 T cell lymphopenia
T– B+ NK–	T– B+ NK+	T– B– NK-	T– B– NK+
IL2RG (SCID-XL)	IL7R	ADA	LIG4
JAK3	CD3δ	AK2 (Reticular dysgenesis)	RAG1
	CD3ε		RAG2
	CD3ζ		DCLRE1C (Artemis deficiency)
	CORO1A		NHEJ1 (Cernunnos XLF)
	PTPRC (CD45 deficiency)		PRKDC (DNA-PKcs deficiency)
	FOXN1
b. Combined Immunodeficiencies (CID) generally less profound than SCID
II. CID with associated or syndromic features
III. Predominantly antibody deficiencies
a. Hypogammaglobulinemia
b. Other antibody deficiencies
IV. Diseases of immune dysregulation
a. Hemophagocytic Lymphohistiocytosis (HLH)
b. EBV susceptibility
c. Syndromes with autoimmunity
d. Immune dysregulation with colitis
V. Congenital defects of phagocyte number, function or both
a. Neutropenia
b. Functional defects
VI. Defects in intrinsic and innate immunity
a. Predisposition to invasive bacterial infections (pyogenes)
b. Predisposition to parasitic and fungal infections
c. Mendelian susceptibility to mycobaterial disease (MSMD)
d. Predominant susceptibility to viral infection
VII. Auto-inflammatory disorders
VIII. Complement deficiencies
IX. Phenocopies of PID

IL2RG, interleukin 2 receptor subunit gamma; JAK3, Janus kinase 3; IL7R, interleukin 7 receptor; CD3δ, CD3δ molecule; CD3ε, CD3ε molecule; CD3ς, CD3ς molecule; CORO1A, coronin 1A; PTPRC, protein tyrosine phosphatase, receptor type C; FOXN1, Forkhead box N1; ADA, adenosine deaminase; AK2, adenylate kinase 2; LIG4, DNA ligase 4; RAG1, recombination activating 1; RAG2, recombination activating 2; DCLRE1C, DNA cross-link repair 1C; NHEJ1, non-homologous end joining factor 1; PRKDC, protein kinase, DNA-activated, catalytic subunit.