summary Eosinophilic Granulomas are self-limiting benign histiocytic lesions that can occur in isolation or as a part of 2 systemic syndromes: Hand-Schuller-Christian (HSC) disease and Letterer-Siwe disease (LSD). Isolated lesions typically present with pain in the thoracic spine or long bones in patients < 20 years of age. HSC presents with diabetes insipidus and exophthalmos, while LSD is fatal in early childhood. Diagnosis is made with biopsy showing mononuclear histiocyte-like cells with oval nuclei with well-defined round cytoplasm with electron microscopy revealing Birbeck granules seen inside Langerhan's cells. Treatment for isolated Eosinophilic Granulomasis is usually observation with pain management as the lesions typically resolve over time. Surgical management is indicated for lesions associated with impending fracture. Treatment for HSC and LSD is focused on the medical management of the syndrome. Epidemiology Demographics most commonly occurs in children (80% of afflicted < 20 years of age) HSC disease presents in children > 3 years of age LSD occurs in children < 3 years of age Male to female ratio of 2:1 Anatomic location eosinophilic granuloma commonly presents in the skull, ribs, clavicle, scapula, mandible isolated lesions of the spine (thoracic most common) can also occur in diaphyseal regions of long bones and the pelvis HSC multiple bony sites multiple lytic skull lesions visceral involvement of the lungs, spleen, liver, skin, lymph nodes Etiology A spectrum of diseases of the reticuloendothelial system with one of three general presentations Eosinophilic granuloma (EG) usually a single self-limited lesion found in younger patients Hand-Schuller-Christian disease (HSC) chronic, disseminated form with bone and visceral lesions also known as Langerhans cell histiocytosis with visceral involvement Letterer-Siwe disease (LSD) fatal form that occurs in young children Genetics no clear genetic pattern of inheritance or locus has been determined Presentation Symptoms skeletal involvement pain and swelling at the region of involvement limping can be seen with pelvic or lower extremity involvement vertebral involvement localized or diffuse back pain increasingly kyphotic posture radiculopathy can occur with more aggressive lesions HSC classic triad of multiple lytic skull lesions diabetes insipidus increased thirst and water intake exopthalmos visceral involvement diffuse or nonspecific abdominal or chest pain Imaging Radiographs general known as "the great mimicker" as it appears similar to many lesions radiographic differential includes osteomyelitis, leukemia, lymphoma, fibrous dysplasia, or Ewing's sarcoma diaphyseal lesions well defined intramedullary lytic or "punched-out" lesion cortex may be thinned, expanded, or destroyed may have periosteal reaction metaphyseal lesions extend up to but not through the physis less central location than diaphyseal lesions spinal lesions vertebra plana (flattened vertebrae) in spine increased kyphosis cranial involvement multiple "punched-out" lytic lesions MRI may show a soft tissue mass adjacent to boney lesions Bone scan generally shows increased uptake in the region of boney lesion Studies Histology Langerhan's cells mononuclear histiocyte-like cells with oval nuclei with well-defined round or oval cytoplasm. a prominent nuclear groove (coffee bean nuclei) can be seen in most of the nuclei eosinophilic cytoplasm (pink generally) stain with CD1A electronmicroscopy birbeck granules seen inside Langerhan's cells mixture of inflammatory cells also present giant cells are present lack of nuclear atypia and atypical mitoses differentiates this condition from malignant conditions such as Ewings sarcoma, lymphoma of bone, and metastatic neuroblastoma, which may look similar based on the round cells alone Differential Eosinophilic Granuloma Differential Destructive lesion in young patients Multiple lesions in young patients Treatment is Observation alone Eosinophilic granuloma o Osteomyelitis o Osteosarcoma o Ewing's sarcoma o Desmoplastic fibroma o Lymphoma o o Leukemia o o Fibrous dysplasia o o Enchondroma / Olliers / Maffucci's o o Osteochondroma / MHE o o Hemangioendothelioma o NOF /Jaffe-Campanacci syndrome o o Paget's o Treatment Nonoperative observation alone indications a self-limited process and it is reasonable to treat with observation alone bracing indications to prevent progressive kyphosis of the spine outcomes will correct deformity in 90% of patients vertebral lesions generally regain 50% of their height low dose irradiation (600-800 cGy) indications indicated for lesions in the spine that compromise stability, neurologic status lesions not amenable to injection or open treatment outcomes effective for most lesions chemotherapy indications diffuse HSC outcomes prognosis is improved with less severe extraskeletal involvement corticosteroid injection indications isolated lesions can be performed after curettage as well Operative curettage and bone grafting indications for lesions that endanger the articular surface or are a risk for impending fractures spinal deformity correction indications progressive spine deformity refractory to bracing approximately 10% of patients with spine lesion will need operative intervention for deformity correction Prognosis EG isolated involvement generally treatable with local management spine lesions can spontaneously resolve HSC prognosis depends on response to chemotherapy worsening prognosis with increasing extraskeletal involvement LSD generally fatal in children < 3 years of age