Mast cells' contribution to the fibrosing alveolitis of the scleroderma lung

Fibrosing alveolitis is frequently seen in scleroderma. Although usually causing progressive symptomatology, it may be found in patients reporting no respiratory symptoms. Mast cells may play a role in the pathogenesis of skin fibrosis in scleroderma. We determined the mast cells and other cellular content, as well as measuring the inflammatory mediators in the bronchoalveolar lavage fluid (BALF) in 17 scleroderma patients and nine control subjects to correlate BALF features with fibrosing alveolitis as determined by lung function testing and high-resolution computed tomographic scans. Bronchoalveolar lavage cells were enumerated after May-Giemsa-Grünwald (MGG), alcian blue, and safranine blue staining. Histamine, tryptase, eosinophil cationic protein, hyaluronic acid, and neutrophil-specific myeloperoxidase were measured by radioimmunoassay. In comparison with normal subjects the BALF of scleroderma patients showed an increased percentage of mast cells (p < 0.002, Mann-Whitney U test), and increased levels of histamine (p < 0.005), tryptase (p < 0.02), and hyaluronic acid (p < 0.004). The BALF of the eight scleroderma patients with an abnormal chest X-ray had a significantly greater number of mast cells (p < 0.04, Mann-Whitney U test), and significantly higher levels of histamine (p < 0.03, Mann-Whitney U test) and tryptase (p = 0.02, Mann-Whitney U test) than the nine scleroderma patients with a normal chest X-ray. This study demonstrates the importance of mast cells and mast-cell activation in the pathogenesis of the fibrosing alveolitis of scleroderma.