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Background: The classification criteria of SSC (EULAR/ACR 2013) compared to the criteria of 1980 showed high sensitivity and allow to detect the full spectrum of systemic sclerosis (SSc). The use of the new criteria led to the fact that some of the patients who were diagnosed with MCTD began to meet the criteria of SSс. Since these patients have hyperproduction of antibodies to RNP, but no other SSc-specific autoantibodies, we believe that they represent a special clinical and immunological phenotype of SSc. Lung involvement in SSc impairеs the quality of life and the prognosis, so the study of interstitial lung disease(ILD)in different phenotypes is relevant.
Objectives: To compare the main manifestations of ILD in two groups of patients who meet the classification criteria of SSc 2013 - positive for a-Topo-1 and for a-RNP.
Methods: The study included 100 patients. The first group - 50 patients positive for a-Topo-1 (45 women and 5 men, mean age 55±10 years, duration of the disease 10.2±8 years, subset of the disease: diffuse 52%, limited 48%) and the second group - 50 patients positive for a-RNP (43 women and 7 men, mean age 44.5±14 years, duration of the disease 11.7±8 years; form of the disease: diffuse 14%, limited 86). The diagnosis of ILD was established by HRCT.
Results: In patients of group I ILD was detected in 94% of cases, in group II - 68% (p<0.05). In both groups a decrease in functional lung tests was noted with a high frequency, but a severe decrease in the lung diffusion capacity was significantly more often observed in group I.
Data of laboratory and instrumental parameters
| Parameters | a-Topo-1- positive
| a-RNP-positive
| p |
| Decrease of DLCO < 80% | 49 (98) | 43 (86) | р<0,05 |
| DLCO <55%, | 33 (66) | 16 (32) | р<0,05 |
| Decrease of FVC< 80 % | 19 (38) | 10 (20) | р<0,05 |
| FVC<70% | 13 (26) | 7 (14) | NS |
| Ground glass opacity | 25 (50) | 26 (52) | NS |
| Honeycombing | 17 (34) | 8 (16) | р<0,05 |
| SPAP >40mm.Hg, | 6 (12) | 10 (20) | NS |
| including PAH** | 2 (4) | 3 (4,6) | NS |
| ANA> 1:640 | 37 (74) | 45 (90) | р<0,05 |
* ANA – antinuclear antibodies, PAH – pulmonary arterial hypertension, SPAP - systolic pulmonary artery pressure ** confirmed by the data of catheterization of the right heart
Typical changes according to HRCT were detected in both groups, but fibrotic changes dominates in group I. There were no significant differences in the frequency of occurrence of PAH. Patients of group II had high level of ANA more often.
Conclusion: In both groups, a high frequency and similar manifestations of ILD were noted. In patients with SSc positive for anti-U1RNP, despite the predominance of limited skin lesions (in 86% of patients), a high incidence of ILD was detected, while the frequency of PAH was comparable to SSc in general. Compared with a-Topo-1 positive patients, ILD was significantly less frequent in anti-U1RNP positive patients and was accompanied with a smaller reduction of DLCO and/or FVC and a lower frequency of severe lung fibrosis. These data confirm the similarity of lung involvement in compared phenotypes of SSc and indicate the importance for screening for ILD in patients with hyperproduction of a-RNP, especially at an early stage of the disease.
REFERENCES:
[1]Van den Hoogen F, Khanna D, Fransen J, et al. 2013 classification criteria for systemic sclerosis: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Ann Rheum Dis 2013;72:1747-55.
Disclosure of Interests: None declared.