Langerhans cell histiocytosis : unusual skeletal manifestations observed in thirty-four cases

Unusual manifestations are occasionally encountered in Langerhans cell histiocytosis and may be a source of confusion. The objective of this study was to determine the frequency of occurrence of the unusual manifestations in our case material. Thirty-four children, average age 4.4 years (range 3 months to 16 years) with 262 skeletal lesions of biopsy-proven Langerhans cell histiocytosis (LCH) were retrospectively reviewed to determine the frequency of occurrence of unusual manifestations defined either as an atypical location of a skeletal lesion or an atypical radiographic appearance of the lesion. Twenty-four unusual lesions were found in this retrospective review. Among these were epiphyseal lesions, transphyseal lesions, extracranial 'button' sequestra, posterior vertebral arch lesions, dural extension of vertebral lesions, and fluid-fluid levels. The finding of fluid-fluid levels has not previously been described in the radiologic literature. Involvement of unusual sites included clavicles and small bones of the hands and feet. Radiographic, computed tomographic, and magnetic resonance imaging of LCH yield a variety of unusual manifestations. Recognition of these varied appearances of LCH may prevent confusion of such appearances with other pathologic processes. When the unusual manifestation occurs as the initial finding of the disease, LCH should be included in the differential diagnosis.