Isolated DLco/VA reduction in systemic sclerosis patients: a new patient subset?

Diffusing capacity for carbon monoxide (DLco) reduction is the first detectable pulmonary functional test (PFT) change in systemic sclerosis (SSc)-related pulmonary complications. reduction in patients without cardiopulmonary alterations has also been observed; a good characterisation of these patients is lacking. The objective of this study is to describe the characteristics of SSc patients with isolated DLco reduction and compare these patients to SSc patients with DLco reduction with a known cause.

SSc patients with DLco < 80% predicted were included and classified into cases (isolated DLco reduction) and controls (DLco reduction in the presence of known pulmonary pathology). SSc clinico-serological data, PFT and echocardiography features were collected and analysed.

From a total SSc cohort of 115 patients, 75 patients were included: 20 cases (26.7%) and 55 controls (73.3%). Cases were predominantly limited skin subset (90% vs 60%, p < 0.001), were anti-centromere antibody (ACA)-positive (95% vs 40%, p < 0.001) and had an infrequent oesophageal involvement (45% vs 74%; p = 0.016). The mean DLco reduction of cases was mild (65.60% ± 10.56). Only 1 out of 20 patients had normal DLco/VA values, and tricuspid regurgitation was more frequent (85% vs 53.8%, p = 0.014).

There is a subgroup of SSc patients with mild isolated DLco and DLco/VA reduction, predominantly limited SSc with ACA seropositivity, which could identify a particular SSc subset. We hypothesise that isolated DLco/VA reduction could indicate a pulmonary vascular involvement. Nevertheless, a close follow-up is mandatory, as a pre-PAH situation cannot be excluded.