Eosinophilic Granuloma
Overview
- Localized form of Langerhans Cell Histiocytosis (LCH)
- Clonal proliferation of Langerhans-type dendritic cells
- Peak incidence: 5–10 years
- Male > Female
- Can be solitary (common) or multifocal
- Non-neoplastic but can be locally aggressive
Histology
- Langerhans cells with grooved nuclei
- CD1a, Langerin, S100 positive
- Electron microscopy: Birbeck granules ("tennis racket" structures)
Systemic Associations
- Solitary EG: typically self-limited
- Multifocal LCH:
- Hand-Schüller-Christian: skull lesions, diabetes insipidus, exophthalmos
- Disseminated LCH (Letterer-Siwe): poor prognosis
Imaging Features
X-ray
Well-defined lytic lesion
- Possible sequestrum or periosteal reaction
Classic Radiologic Appearances
- Vertebra plana
- Flattened vertebral body with preservation of posterior elements
- Most common cause of vertebra plana in children
- Beveled edge skull lesion
- Lytic lesion with asymmetric destruction of inner and outer tables
- May show soft tissue mass
- Floating tooth
- Lytic alveolar ridge lesion leading to apparent dental loosening
- Mandible > maxilla
MRI
- T1: hypointense
- T2/STIR: hyperintense with marrow and soft tissue edema
- Post-Gd: enhancement often more dramatic than symptoms
Bone scan
- Increased uptake
- Useful in detecting multifocal lesions
Differentials
Vertebra plana (MELT)
| Mnemonic | Cause |
|---|---|
| M | Mets / Myeloma |
| E | Eosinophilic Granuloma |
| L | Lymphoma / Leukemia |
| T | Trauma / TB |
Diagnostic Tips
- Vertebra plana in child → EG until proven otherwise
- Beveled skull lesion in child = classic
- Floating tooth sign = alveolar EG
- May mimic Brodie abscess or malignancy but lacks systemic signs
- Aggressive MRI appearance can be misleading
