Serodiscordant patients with systemic sclerosis: when antibody does not correspond to skin involvement

Diffuse cutaneous systemic sclerosis (dcSSc) is associated with anti-topoisomerase (ATA) whereas limited cutaneous (lcSSc) and sine scleroderma (ssSSc) are mainly associated with anti-centromere antibody (ACA). Serodiscordant patients were defined as lcSSc subjects with ATA, dcSSc with ACA, and ssSSc with ATA. The aim of the present study was to compare the clinical manifestations and prognosis between serodiscordant patients and their counterparts (those with lcSSc with ACA, dcSSc with ATA and ssSSc with ACA, respectively).

From the Spanish Scleroderma Registry we selected those patients for whom skin involvement (dcSSc, lcSSc or ssSSc) was detailed at baseline and last visit and ACA and ATA had been determined. Demographic, clinical characteristics, and survival data were compared according to the antibody status.

The whole cohort comprised 901 patients and six mutually exclusive groups were defined: lcSScACA in 511 (57%) patients, lcSScATA group in 87 (10%), dcSScATA group in 172 (19%), dcSScACA group in 21 (2%), ssSScACA group in 92 (10%), and ssSScATA group in 18 (2%) patients, respectively. Interstitial lung disease (ILD) and severe ILD were more frequent in patients with dcSScATA than in those with dcSScACA. Conversely, the prevalence of isolated pulmonary hypertension (without ILD) was higher in those with dcSScACA (15% vs. 2%; p=0.018). No differences were found regarding survival when comparing serodiscordant patients with the seroconcordants patients.

In our cohort, the prevalence of serodiscordant SSc patients was low. They differed from their counterparts in some clinical manifestations. The management of patients with SSc should be guided by both serology and cutaneous subtype.