 Mutations in HLA genes seem to play a crucial role in the pathogenesis of some cases (but not all), likewise silica, aromatic and chlorinated solvents, ketones, trichloroethylene, welding fumes and white spirits exposure seems to contribute to the condition in a small proportion of affected persons.It is characterised by increased synthesis of collagen (leading to the sclerosis), damage to small blood vessels, activation of T lymphocytes and production of altered connective tissues.Its proposed pathogenesis is the following