The acquired hyperostosis syndrome: a little known skeletal disorder with distinctive radiological and clinical features.

The acquired hyperostosis syndrome (AHS) is a chronic inflammatory disorder of bone of unknown etiology. It is accompanied by circumscribed hyperostosis which can be associated with ossifying lesions at sites of tendinous and ligamentary insertions and erosive or non-erosive arthritis. The predominant location of lesions is the sternocostoclavicular region (approximately 80% of patients), less frequent are involvement of the spine, pelvis, and appendicular skeleton. In 20%-60% of cases AHS is associated with palmoplantar pustulosis, psoriasis, or severe acne (acne fulminans or conglobata). The X-ray appearance of AHS is a more or less homogeneous increase in density with blurred margins, which on scintiscan with labeled phosphate compounds is associated with intense accretion of tracer. These features are associated with a variable increase in the acute phase reactants and a conspicuously low increase, if any, in serum alkaline phosphatase. The therapeutic modalities which have been used so far are entirely symptomatic. Long-lasting improvement has been reported following percutaneous anti-inflammatory radiation therapy.