Teaching Case

Complaints of increasing pain at the left elbow, especially at night. No fever or malaise. No history of trauma or other relevant disease. Laboratory tests were normal.

A four-year-old boy presented with complaints of increasing pain at the left elbow, especially at night. No fever or malaise was present. Previous medical history revealed no trauma or other relevant disease. Laboratory tests showed a normal blood count and a normal sedimentation rate. Two radiographs of the left elbow were performed within two weeks. Subsequently CT scan and MRI were carried out. The final diagnosis was established by open biopsy. The imaging findings, especially the appearance on conventional radiographs with pronounced new bone formation, are suggestive for a neoplasm (Ewing's sarcoma, acute lymphoid leukemia, non Hodgkin lymphoma) histiocytosis X, or osteomyelitis. Histological examination of a biopsy specimen revealed Langerhans'cell histiocytosis or eosinophilic granuloma.

Langerhans'cell histiocytosis (LCH), formery known as Histiocytosis X, is an idiopathic non neoplastic proliferation of histiocytes that may have a localized or systemic clinical manifestation. The cause of LCH is unknown. The localized form of LCH of bone or lung accounts for 60 to 80 percent of all cases. Although LCH of bone is the most common form, it has an incidence of only 1-2 cases per million per year. It has a peak incidence between the age of 5 and 15 years. The male-to-female ratio is approximately 1:2. Most but not all bony lesions are symptomatic, usually characterized by local pain, swelling and tenderness. Generally, the duration of symptoms is short, less than 2 months. LCH may involve any bone, however the preferred sites are the skull, mandible, spine and long bones. Long-bone involvement, especially of the femur and tibia, is more frequently seen in children. In the long bones, lesions usually arise in the diaphysis or metaphysis. They are initially situated in the medullary cavity and cause endosteal scalloping with cortical thinning and/or erosion. The margins of the lesion are poorly defined but may later become sharply defined or sclerotic. The amount of associated periosteal reaction is variable but may be quite extensive. Lamellated or solid reaction is typical. Clinical and laboratory examination in combination with conventional radiographs and MRI frequently lead to a correct diagnosis.