Table 2.

Inborn errors of PDCD1 and their phenocopies.

	Genetic PD-1 deficiency				PD-1 or PD-L1 immune checkpoint inhibitor
Main clinical phenotypes		%	Immune/histological phenotype	Ref.	All (%)	Grade 3-5(%)	Immune/histological phenotype	Ref.
	Dermatologic manifestation	Present*	Impaired IFN-γ production by T cells. Decreased Vδ2+ γδ T cells, mucosal-associated invariant T cells, and CD56bright natural killer cells. Increased CD4- CD8- double-negative αβ T cells.	(96)	16-50%	<3%	Dermatologic: Increased serum IL-6 and skin CD8/CD4 ratio. Gastrointestinal: Neutrophilic and lymphocytic inflammation. Liver: lymphocyte infiltration and rare plasma cell and eosinophil.	(28, 97–100)
	Thyroid diseases	Present			8-24.5%	<1%		(28, 98, 101–105)
	Gastrointestinal manifestation	Not described			1-20%	1-2%		(98, 102, 105–107)
	Respiratory tract manifestation	Present			2.2-16%	1-2%		(98, 101, 102, 105)
	Liver manifestation	Present			5.2-18%	<1%		(98, 103, 108)
	Type 1 diabetes	Present			<1%	<1%		(28, 101, 104)
	Tuberculosis	Present			–			–

* - Only one child with inherited PD-1 deficiency is described yet.