Massive accumulation of osteoclastic giant cells in rapid destructive hip disease.

The term rapid destructive hip disease (RDHD) designates a rare coxarthropathy characterized by a rapid destruction of the femoral head within a few weeks to several months. The etiology and pathogenesis of RDHD are not understood. The goal of this study was to define the histological and histomorphometric hallmarks of RDHD to provide a basis for a deeper understanding of the underlying mechanisms. Fifteen consecutive RDHD patients (mean age 78.9 ± 6.4 years, 14 females) demonstrated the characteristic radiographic appearance of vanishing femoral head bone stock without signs of reactive anabolic changes. Histologic and histomorphometric analyses revealed severe bone resorption with significantly increased numbers of morphologically altered giant osteoclasts, the formation of giant cell granulomas both in bone marrow and the synovium and significantly increased osteoblast numbers and osteoid as compared to controls with primary osteoarthritis (OA). These results suggest that in RDHD, an unknown stimulus leads to a massive activation of osteoclasts and this in turn provokes a reactive increase in osteoblast activity that is too weak to counteract the rapid destruction of the hip, thus providing a rationale for a prospective systematic search for the stimuli upstream of the massively increased osteoclast activation in RDHD.