Eosinophilic Granuloma

Excerpt

Eosinophilic granuloma (EG) is the mildest variant of Langerhans cell histiocytosis. In 1940, Lichtenstein and Jaffe first introduced the term EG. Lichtenstein in 1953 included eosinophilic granuloma, Hand-Schuller-Christian disease, and Letterer-Siwe disease under the disorder histiocytosis X referring to the proliferation of histiocytes (Langerhans cells) due to an unknown etiology. They are now known as Langerhans cell histiocytosis (LCH). EG is a benign tumor-like disorder characterized by abnormal proliferation of antigen-presenting cells of dendritic origin known as Langerhans cells. These Langerhans cells originate from meloid dendritic cells rather than skin. EG is the most common form of Langerhans cell histiocytosis.

The disease mostly affects the axial skeleton, namely skull, jaw bone, spine, pelvis, ribs, and long bones. Lesions in the long bones are primarily located in the diaphysis. It frequently involves the soft tissues adjacent to the bone. The site of bone involvement is different in children and adults. In children most commonly involved bone is the skull (frontal bone), in contrast to adults, where the jaw is more frequently involved. The thoracic spine is most often involved in children as opposed to the cervical spine in adults. Other less commonly affected sites include the skin, pituitary gland, lung, brain, liver, spleen, and the gastrointestinal tract. EG accounts for less than 1% of all bone tumors. The presentation of EG is either solitary, which rarely requires treatment or multisystem, which requires aggressive therapy.

Langerhans Cell Histiocytosis Classification

1. Eosinophilic Granuloma:

   1. Single bone lesion (Monostotic): More common and seen in nearly 90% of patients.

   2. Multiple bone lesions (Polyostotic): Less common and seen in nearly 10% of patients.

2. Hand-Schuller-Christian Disease: Characterized by a classic triad of exophthalmos, diabetes insipidus, and osteolytic skull lesions.

3. Letterer-Siwe Disease: Characterized by lymphadenopathy, skin rash, hepatosplenomegaly, and pancytopenia.