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
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
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