Table 2.

Most common auto‐Ab associations in the major CTD

CTD	Auto‐Ab	Clinical associations
Systemic sclerosis	ANA
	Anti‐centromere	Strong association with PAH; ‘limited’ disease
	Anti‐Scl 70 (topoisomerase I)	Strong association with ILD; ‘diffuse’ disease
	Anti‐RNA polymerase I, III	Increased risk of renal crisis with concomitant corticosteroid use Not included on most ENA panels
RA	RF
	Anti‐CCP	Strong association with RA‐ILD
Idiopathic inflammatory myositis	ANA Myositis‐specific Ab: Anti‐tRNA synthetase (Jo‐1, PL7, PL12, EJ, OJ)	Associated with high prevalence of ILD
	MDA5	May be associated with rapidly progressive ILD
	Mi2, TIF1y, NXP2, SAE	TIF1y, NXP2 increased risk of malignancy
	SRP, HMGCR	IMNM; severe muscle disease
	Myositis‐associated Ab: PM‐Scl, Ro52, Ku	Also detected in other CTD
Systemic lupus erythematosus	ANA	Present in >95% of cases
	Anti‐dsDNA	Titre often correlates with disease activity
	Anti‐Sm, ‐RNP, ‐ribosomal P
	Anti‐Ro60 (SSA), ‐Ro52, ‐La (SSB)
Sjögren's syndrome	ANA
	Anti‐Ro60 (SSA), ‐Ro52, ‐La (SSB)	Some patients may have a positive RF
Mixed connective tissue disease	ANA
	Anti‐RNP

Ab, antibody; ANA, anti‐nuclear antibody; CCP, cyclic citrullinated peptide; CTD, connective tissue disease; dsDNA, double‐stranded DNA; ENA, extractable nuclear antigen; ILD, interstitial lung disease; IMNM, immune‐mediated necrotizing myopathy; NXP, nuclear matrix protein; PAH, pulmonary arterial hypertension; PM, polymyositis; RA, rheumatoid arthritis; RA‐ILD, RA‐associated ILD; RF, rheumatoid factor; RNP, ribonucleoprotein; SAE, serious adverse event.