MAST-CELLS CONTRIBUTION TO THE FIBROSING ALVEOLITIS OF THE SCLERODERMA LUNG

Fibrosing alveolitis is frequently seen in scleroderma. Although usual ly causing progressive symptomatology, it may be found in patients rep orting no respiratory symptoms. Mast cells may play a role in the path ogenesis of skin fibrosis in scleroderma. We determined the mast cells and other cellular content, as well as measuring the inflammatory med iators in the bronchoalveolar lavage fluid (BALF) in 17 scleroderma pa tients and nine control subjects to correlate BALF features with fibro sing alveolitis as determined by lung function testing and high-resolu tion computed tomographic scans. Bronchoalveolar lavage cells were enu merated after May-Giemsa-Grunwald (MGG), alcian blue, and safranine bl ue staining. Histamine, tryptase, eosinophil cationic protein, hyaluro nic acid, and neutrophil-specific myeloperoxidase were measured by rad ioimmunoassay. In comparison with normal subjects the BALF of sclerode rma patients showed an increased percentage of mast cells (p < 0.002, Mann-Whitney U test), and increased levels of histamine (p < 0.005), t ryptase (p < 0.02), and hyaluronic acid (p < 0.004). The BALF of the e ight scleroderma patients with an abnormal chest X-ray had a significa ntly greater number of mast cells (p < 0.04, Mann-Whitney U test), and significantly higher levels of histamine (p < 0.03, Mann-Whitney U te st) and tryptase (p = 0.02, Mann-Whitney U test) than the nine sclerod erma patients with a normal chest X-ray. This study demonstrates the i mportance of mast cells and mast-cell activation in the pathogenesis o f the fibrosing alveolitis of scleroderma.