[Plasma cell dyscrasias and diffuse idiopathic skeletal hyperostosis. Is it a merely accidental association?]

The radiologic staging of a series of 144 patients (88 males and 56 females) affected with plasma-cell dyscrasias and observed over a 26-month period, revealed both the well-known bone myeloma-related abnormalities and hyperostotic lesions similar to those described in diffuse idiopathic skeletal hyperostosis. The incidence of skeletal hyperostosis was 31.94%, much higher than that reported in literature for the general population (5%). Typically, the axial skeleton is the most common location for abnormalities in multiple myeloma (MM) as well as in DISH: involvement of the dorsal spine was observed in 65% of cases, the cervical spine was involved in 34.8% of patients, and the lumbar spine in 28.3%. Peripheral ossifying enthesopathy, considered as "whiskering" in the pelvis, was found in 12 cases (8.2%), 7 males and 5 females. DISH was indifferently present in both MM (23 cases), with severe osteolysis (stage III) or simple osteoporosis (stage I), and monoclonal gammopathy of undetermined significance (MGUS) (17 cases), usually without any myeloma-related bone lesions, and in Waldenström disease (4 cases). Many hypotheses are discussed as to the possible pathogenesis (e.g.: accidental, dysmetabolic, or degenerative) of hyperostosis in dysgammaglobulinemias, but, to date, they are no more than mere guesses. DISH is a disorder the etiology of which is still unknown: it is likely to be an ossifying diathesis, but its incidence in both illnesses--which are both plasma-cell dyscarsias--is too high for the association to be accidental. Thus, a pathogenetic factor produced by multiple myeloma can be hypothesized, capable of increasing the so-called idiopathic hyperostosis.