Premalignant conditions of bone

Werner, Rothmund-Thompson, and Bloom syndromes all present with characteristic cutaneous findings during childhood and a predisposition for highgrade osteosarcoma, often at unusual locations, such as the patella. Although each of these syndromes maps to a unique genetic locus, the gene products share significant sequence homology. The latter finding is intriguing given the clinical similarities between the syndromes. Osteosarcoma is typically a diagnosis of childhood among the congenital syndromes. In contrast, chondrosarcoma presenting as part of an inherited syndrome does so late in adult life and is discussed in the context of specific precursor lesions below.