Mixed Connective Tissue Disease and Overlap Syndromes

Mixed Connective Tissue Disease and Overlap Syndromes 

In longitudinal studies, the lung has been involved in 20% to 85% of patients (320,321). Approximately two thirds of asymptomatic patients have reduced DLco. chest radiographic abnormalities, or both (322), and nearly half have a restrictive ventilatory defect (321,322). In a retrospective study of 144 consecutive patients with MCTD, ILD was seen on HRCT in 66.6% of cases (324), with more severe fibrosis occurring when SSc was the predominant clinical feature (321). 

There is a paucity of histological data, based on the ATS/ERS classification of IIPs, with NSIP reported in a handful of cases (4). Early signs on HRCT in early include areas of ground-glass attenuation, alone (78%) or in association with mild reticular abnormalities (22%) (Fig. 15) (324,325). In later disease, honeycombing is exceedingly rare, even when fibrosis is extensive (324-326). The distribution on HRCT is predominantly basal, peripheral, and posterior. 

In the retrospective study of Bodolay et al. (324), patients with MCTD-ILD received high-dose steroid therapy for four to six weeks (324). HRCT abnormalities regressed in approximately 50%, with little change in PFTs. In the remaining patients, a combination of corticosteroids and cyclophosphamide was highly efficacious, with HRCT appearances reverting to normal in 70% of cases and mild residual pulmonary fibrosis in 30% (324). 

Among overlap syndromes, ILD seems to be particularly frequent in patients with sclero(dermato)myositis. Sclero(dermato)myositis differs from MCTD by the absence of features of SLE (327). The anti-PM/Scl antibody is characteristic, although also found in PM, DM, or SSc without feamres of overlap syndromes (328). The reported prevalence of ILD in patients with this antibody is variable, reaching 85% in one series (Fig. 16) (329). Despite the high frequency of ILD, patients with the anti-PM/Scl antibody have a favorable outcome (329). 

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VIII. Mixed Connective Tissue Disease and Overlap Syndromes... 

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