Tsk1/+ mice exhibit skin, tendon and cardiac fibrosis, and autoimmunity with extensive B cell activation and autoantibody formation, but also develop phenotypes that differ from human SSc, including hypodermal collagen accumulation (Baxter et al., 2005) and an emphysema-like lung pathology (Box 1) (Rossi et al., 1984). The gene discussed is TSSK1B; the disease is systemic sclerosis.