Characteristics

• Poorly understood spectrum of conditions.

• Characterised by proliferation of Langerhans cells (similar to mononuclear macrophages).

• Can occur at any age; most present in childhood.

• Sub-divided into eosinophilic granuloma (80%), Hand–Schüller–Christian disease (10%) and Letterer–Siwe disease (10%).

Clinical features

• Eosinophilic granuloma – relatively benign. Often presents with non-specific bone pain in the 5–10 year age group.

• Letterer–Siwe disease – acute disseminated form tends to present early in infancy with wasting, hepatosplenomegaly and lymphadenopathy. Pancytopenia common.

• Hand–Schüller–Christian disease – chronic form. Presents in the 5–10-year-old group with diabetes insipidus, exopthalamos and lytic skull lesions.

Radiological features

• Lesions are usually well defined with a lucent centre and serrated and bevelled edge. A sclerotic margin is seen in the healing phase. True expansion is rare.

• Lesions common in skull and axial skeleton.

• Skull lesions often appear ‘punched out’ and may coalesce to form a geographical pattern. Differential inner- and outer-table involvement may give the appearance of a hole within a hole.

• Vertebrae plana – vertebral bodies appear flattened with a preserved disc height.

• Long bones – usually diaphyseal, respecting the epiphyseal plate and joint. Again, lytic with a sclerotic rim.

• Mandibular involvement can lead to the appearance of ‘floating teeth’.

Management

• Orthopaedic management generally targete0d to obtaining a definitive tissue diagnosis.

• If accessible, excision/curettage or radiotherapy should be considered.

• Chemotherapy for aggressive forms.