Hyperostosis

A widespread form of hyperostosis characterized by flowing calcification and ossification of vertebral bodies occurs in diffuse idiopathic skeletal hyperostosis DISH . Radiographic abnormalities are observed most commonly in the thoracic spine. In this disease, calcification and ossification may lead to the presence of a radiodense shield in front of the vertebral column. Enthesophytes are frequently seen on various bone surfaces.

Calvarial hyperostosis occurs in various pathologic conditions, including Pagets disease, hyperostosis frontalis interna, frontometaphyseal dysplasia, fibrous dysplasia, anaemia, craniodiaphyseal dysplasia and skeletal metastasis.

Endosteal hyperostosis has three subtypes, van Buchems syndrome, sclerosteosis and Worths syndrome. In Van Buchem's syndrome, severe enlargement of the mandible, cranial nerve involvement, a prominent forehead and widened nasal bridge, periosteal excrescences in the tubular bones, osteosclerotic and enlarged ribs and clavicles, and increased radiodensity of the spine are characteristic. In sclerosteosis patients may have excessive height and weight, peculiar facies, hypertelorism, deafness, facial palsy, syndactyly of fingers, absent or dysplastic nails, and radial deviation of the terminal phalanges. On radiographs a progressive marked hyperostosis of the skull and mandible is seen. In Worth's syndrome, enlargement of the jaw and the presence of a palatal mass (torus palatinus) are important clinical signs. Radiographically, cortical thickening in the tubular bones without expansion or abnormal modeling is observed.

Infantile cortical hyperostosis, also known as Caffeys disease, is characterized by soft tissue nodules, periostitis and hyperostoses. Bones (mandible, clavicle, scapula, ribs, tubular bones) and adjacent fasciae, muscles and connective tissues are affected. The most prominent feature of the disease, cortical hyperostosis, begins as a soft tissue swelling directly contiguous to the bone cortex and may lead to doubling or tripling of the normal width of the bone. Destructive lesions of the skull or tubular bones have also been identified.

Sternocostoclavicular hyperostosis is characterized by distinctive bone overgrowth and soft tissue ossification of the clavicle, anterior portion of the upper ribs and sternum. Bone overgrowth may lead to occlusion of the subclavian veins. The major radiographic abnormalities are seen in the anterior and upper portion of the chest wall and vertebral column. Spinal outgrowths may be seen that resemble those of ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis or psoriatic spondylitis.

Vitamin A intoxication and long-term use of isotretinoin have also been associated with skeletal hyperostosis (see hypervitaminosis A).

Various groups of disorders characterized by hyperostosis, osteitis and skin lesions h have been termed the SAPHO syndrome. This term also encompasses sternocostoclavicular hyperostosis, arthro-osteitis associated with pustulosis palmaris et plantaris, and arthro-osteitis associated with severe acne. Bone sclerosis is a dominant radiographic abnormality.

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