Purpose: The aim of this study was to evaluate whether pulmonary microvascular damage is part of a more generalized involvement of the microvasculature in the spectrum of scleroderma (Scl)-like syndromes.
Patients and methods: We studied four groups of patients, all with Raynaud's phenomenon (RP), distinguished by the extent and nature of their underlying connective tissue disease. Twenty-two patients had primary RP (pRP), another 22 patients had RP and an undifferentiated connective tissue disease (uCTD), 15 patients had Scl, and eight patients had the CREST syndrome (CREST). Pulmonary vascular damage in these groups was assessed by measuring the pulmonary diffusing capacity (T1,CO) and its components: the diffusing capacity of the alveolocapillary membrane (Dm) and the pulmonary capillary blood volume (Vc). Results were compared with morphologic abnormalities of the nailfold capillaries, as determined by nailfold capillary microscopy, and related to the presence of antinuclear antibodies.
Results: Vc was below normal in 38% and 43% of patients with pRP and uCTD, respectively (versus 52% in patients with Scl or CREST combined). In contrast, Dm was below normal in only 5% and 26% of patients with pRP and uCTD, respectively (versus 61% in patients with Scl or CREST combined). In patients with Scl and CREST, Dm was significantly decreased as compared with the former groups (p less than 0.01). Dm was also the pulmonary function parameter that correlated most strongly with both nailfold capillary abnormalities and the presence of antinuclear antibodies, whereas Vc did not.
Conclusion: Early pulmonary involvement in Scl syndromes is functionally characterized by a lowered Dm, correlating with morphologic changes of the nailfold capillaries. Decreased Vc is probably a reflection of RP of the pulmonary vasculature.