Eosinophilic Granuloma

   Eosinophilic granuloma (EG) is a solitary, non-neoplastic proliferation of histiocytes. EG is part of a spectrum of Langerhan's cell histiocytosis, formerly known as histiocytosis X. EG is a localized lesion in bone or lung and occurs most commonly in children aged 5 to 10. It makes up 60-80% of all cases of Langerhan's cell histiocytosis and is uncommon in blacks. EG is found in the skull, mandible, spine and long bones. The male to female ratio is two to one. Letterer-Siwe disease is a fulminant systemic disease that comprises 10% of Langerhan's cell histiocytosis, occurs in children under 3 years old and is rapidly fatal. Hand-Schuller-Christian disease (HSC) is a chronic disseminated form of Langerhan' s histiocytosis and occurs in older patients. The well known triad of HSC is diabetes insipidus, exopthalmos and skull lesions.   EG can convert to systemic forms of the disease.
   EG is normally symptomatic. Local pain, swelling and tenderness are common and the ESR may be elevated.
   The radiologic appearance of EG is non-specific and differs by location. The skull may have a lesion with sharp, punched out borders that is uneven across the inner and outer table causing a "beveled edge". Pelvic lesions are often poorly defined. Spine lesions are normally found in the vertebral body. EG is found in the diaphysis or metaphysis of long bones in the center of the medullary cavity. The lesion may cause endosteal scalloping or a periosteal reaction. Bone scan is not useful in defining EG. CT scan and MRI delineate the extent of the intramedullary and cortical penetration. The radiologic differential includes Ewing's sarcoma, osteosarcoma, metastases and osteomyelitis.
   On gross examination, EG is a soft, granular or gelatinous mass. It appears gray red to brown with flecks of yellow.
   Under the microscope, EG consists of sheets of Langerhan's cells. These cells are derived from the mononuclear cell and dendritic line precursors and are found in the bone marrow. The cell is identifiable under the electron microscope as the Langerhan's cell has racket shaped cytoplasmic inclusion
bodies called Birbeck's granules. Also present in the lesion are varying amounts of lymphocytes, polymorphonuclear cells, eosinophils and giant cells. Early lesions have many Langerhan's cells and eosinophils. Older lesions have fewer cells and much fibrous tissue. The cause of EG is unknown and speculated to be either infection or immunological.
   Treatment of EG depends on the form of the disease. With localized disease, often a biopsy alone is enough to incite healing. Other treatment modalities of EG include curettage, excision, steroid injection, radiation and observation. ' . Chemotherapy is recommended for systemic disease.

' Mackenzie, WG and KS Morton, Eosinophilic Granuloma of Bone, The Canadian Journal of Surgery, 31(4):264-267, July, 1988.

Greis, PE and FM Hankin, Eosinophilic Cranuloma, Clinical Orthopaedics and Related Research, 257:204211, August, 1990.

Conway, WF and CW Hayes, Miscellaneous Lesions of Bone, Radiologic Clinics of North America, 31(2): 339-357, March, 1993.

Bulloughs, Peter. Orthopaedic Pathologv (third edition), Times Mirror International Publishers Limited, London, 1997. Huvos, Andrew. Bone Tumors: Diagnosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.










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