Table 2.

Monogenic forms of SLE

Disease	Gene		Protein function	Inheritance	Clinical presentation
Monogenic SLE	TREX1		3′-5′ DNA exonuclease	AD (AR in few cases)	SLE
	C1q	C1qA	Central pattern-recognition molecule in the classical pathway of the complement system	AR	SLE, membranous proliferative GN, arthritis, bacterial infections
		C1qB
		C1qC
	C1r		Components of the C1 complex in the classical pathway of the complement system	AR	SLE, RA-like arthritis, sinopulmunary infections
	C1s				SLE, Hashimoto’s thyroiditis, autoimmune hepatitis
	C2		Component of the classical pathway of the complement system	AR	SLE in a minority of affected individual. Arthritis, malar rash, discoid rash.
	C3		Major complement component, involved in all three pathways of activation	AR	Upper and lower respiratory tract infection, SLE in a minority of affected individual.
	C4A		Component of the classical pathway of the complement system	AR	SLE, type 1 diabetes mellitus, glomerulonephritis
	Dnase1		Endonuclease present in tissues, serum and body fluids	AD	SLE, Sjögren syndrome, antinucleosomal autoantibodies
	DNase1L3		Endonuclease, homologue to Dnase1	AR	Pediatric onset SLE, lupus nephritis, hypocomplementemic urticarial vasculitis syndrome HUVS.
	ACP5		Lysosomal phosphatase activity	AR	Skeletal dysplasia (SPENCD), SLE, Sjögren syndrome, Raynaud
	PRKCD		Serine/threonine kinase implicated in the control of cell proliferation and apoptosis	AR	Pediatric onset SLE, lupus nephritis
	IFIH1		Cytosolic receptor for dsRNA	AD	SLE with IgA deficiency, mild lower limb spasticity
Chilblain lupus	TREX-1		3′-5′ DNA exonuclease	AD	Chilblain lesions, skin ulcers, loss of ear cartilage
	SAMHD1		Restricts the availability of cytosolic deoxynucleotides	AR and AD	Chilblain lesions, photosensitivity

AD autosomal dominant, AR autosomal recessive, GN glomerulonephritis, ACP5 Acid Phosphatase 5, Tartrate Resistant, HUVS Hypocomplementemic urticarial vasculitis syndrome, IFIH1 IFN-induced helicase C domain-containing protein 1 (also known as MDA5), PRKCD Protein Kinase C Delta, SAMHD1 deoxynucleoside triphosphate triphosphohydrolase SAM domain and HD domain 1, TREX1 DNA 3ʹ repair exonuclease 1