Additional changes may occur in the vertebral column, which include syndesmophytes, para-articular osseous bridging, and erosions that resemble ankylosing spondylitis including the sacroiliac joints, diffuse idiopathic skeletal hyperostosis, or psoriatic spondylopathy. “Ivory vertebrae” resembling metastases may also be seen. Swelling, tenderness, and pain on movement are documented in extra-axial locations, but radiographic findings are usually only of soft-tissue swelling, without erosive change. Periosteal proliferation and sclerosis have been identified in long tubular bones.5–
Sternocostoclavicular hyperostosis is one of a group of conditions that feature hyperostosis, often associated with cutaneous abnormalities within the SAPHO syndromes (synovitis, acne, pustulosis, hyperostosis, osteitis). These syndromes include chronic recurrent multifocal osteomyelitis that is seen in the pediatric population and may show similar changes of hyperostosis. Cutaneous changes may be seen in sternocostoclavicular hyperostosis in the form of palmoplantar pustulosis, which is present in 30 to 50% of patients, typically within 2 years before or after but more often simultaneously with the skeletal manifestations.6–
To further confuse potential etiologies, identical lesions are present with chronic recurrent multifocal osteomyelitis, another condition that causes clavicular hyperostosis.7–
Histologic examination from bone biopsies of ossified thoracic masses resemble Paget disease with dense fibrosis and bone formation, granulation tissue, and round cell infiltrates.8
The majority of cultures are sterile.