[The acquired hyperostosis syndrome. 2].

In the second part of this publication, we describe some additional findings in cases of sternocostoclavicular hyperostosis. These include focal hyperostosis of the spine, in the pelvis and in the extremities and psoriatic skin lesions and severe forms of acne (acne conglobata, acne fulminans). Other features, which are not diagnostic, include erosive or non-erosive peripheral arthritis and unilateral or bilateral sacro-iliitis. An analysis of our 13 patients and of the relevant literature indicates that the hyperostosis is due to increased bone metabolism and heterotopic ossification of fibrous tissue and that these are the pathogenic bases of the changes in the axial skeleton, the pelvis and the bones of the extremities. We have suggested a scheme which would categorize the syndrome into complete, incomplete and possibly acquired forms.