Erosive Inflammatory Pseudotumor of the Odontoid Process in Association With Forestier's Disease (Diffuse Idiopathic Skeletal Hyperostosis)

Abstract not available. Introduction provided instead.

Inflammatory pseudotumor, first described in 1954,¹ was initially considered any lesion that simulated a neoplastic condition at clinical, macroscopic, and microscopic levels but that was thought to have an inflammatory and/or reactive pathogenesis. In recent literature, inflammatory pseudotumor is mostly considered a mass lesion characterized microscopically by a proliferation of a spindle-cell component against a heavy inflammatory infiltrate of mixed composition but usually with a predominance of mature lymphocyte and plasma cells.²

The World Health Organization accepts the term inflammatory myofibroblastic tumor, but, given the heterogeneity of these soft-tissue tumors, other terms, based on original body sites, are still applied.³ This naming convention reflects the complexity and variable histologic characteristics and behavior of the entity. Pseudotumors are important at least because of their ability to mimic malignant tumors, either clinically or radiologically.^4-6 Inflammatory pseudotumors can develop in many sites but is most commonly reported in the lung, orbit, gastrointestinal tract, and kidney.^4,7 The spinal column is an extremely rare site for pseudotumors; to our knowledge, only 16 cases have been reported,^4,8-20 the last in 2005.⁴ Four cases in the periodontoid area were reported.²¹ The lesion was associated with diffuse idiopathic skeletal hyperostosis (DISH) in only 1 case, reported by Jun and colleagues.¹⁹ To the authors’ knowledge, atlantoaxial dislocation resulting from periodontoid pseudotumor in association with Forestier’s disease has not been previously reported.

DISH was first described in 1950 by Forestier and Rotés-Querol²¹ as senile ankylosing hyperostosis of the spine, but soon it was discovered that this disorder is not limited to “senile” age groups and is not limited to the “spine,” ie, there are many cases of the disorder among younger age groups and/or those with extraspinal manifestation. However, this condition, now also known as Forestier’s disease, has a marked predilection for the axial skeleton, particularly the thoracic and lumbar spine. Although DISH is considered a benign rheumatologic disorder, it can be associated with a variety of complications ranging from pain and stiffness to different neurologic disturbances and even dysphagia.^19,22