Solitary eosinophilic granuloma of the radius

Clinical History

1 year old male child presented with a swelling in the right fore arm of 1 week duration

Imaging Findings

This 1-year-old boy presented with a week’s history of swelling and deformity in his right forearm. The X-ray revealed a lytic lesion in the proximal end of the radius with a fracture through it. MRI scan of the forearm confirmed the presence of bone destruction and of a soft tissue mass extending distally down the radius for about two thirds of the arm. Axial slices showed infiltration of the surrounding tissue by the mass with periosteal new bone formation. The Subcutaneous tissue was well preserved. A biopsy was taken and the histopathological examination showed a typical appearance of Langerhans-cell histiocytosis. Skeletal survey showed no other bone or joint involvement. There was no evidence of visceral involvement. This was consistent with a diagnosis of eosinophilic granuloma. He was treated with an intralesional injection of a high dose of methylprednisolone and immobilisation. The lesion completely healed in 8 months, enabling full range of movement of his right elbow.

Discussion

Langerhans-cell histiocytosis comprises of a group of disorders characterized by the proliferation of Langerhans-cell histiocytes, which are dendritic cells found in normal tissues. The common sites of soft tissue involvement include the skin, pituitary stalk, lung, liver and the spleen. Lesions in the bone commonly occur in the skull, spine, pelvis, ribs and the femur. Eosinophilic granuloma, which is the most benign end of the spectrum is one such disorder, which only involves the bone. The other conditions are Letterer-Siwe disease, Hand-Schuller-Christian syndrome and Hishimoto-Pritzker syndrome. The bone lesions may be asymptomatic or may present with swelling, pain or pathological fracture. Skull lesions have a well-defined, punched-out appearance. Vertebra plana is the typical spinal lesion, where the vertebral body is markedly collapsed, but the adjacent disc space is preserved and there is no cord compression. This usually affects one vertebral body. The typical long bone lesion is lytic and is located in the diaphysis or the metaphysis. Other X-ray findings include endosteal scalloping, cortical thickening and widening of the medullary cavity. Differential diagnoses include Ewing sarcoma and osteomyelitis. Lamellated periosteal elevation may be seen in all the three (5 % of the solitary eosinophilic granuloma). MRI changes are non-specific and do not differentiate the above. Definitive diagnosis requires electron microscopy demonstration of Birbeck granules in lesional histiocyte or the presence of specific immunochemical markers. A bony lesion which usually presents with pain, without soft tissue involvement is the most common presentation and has the best prognosis. A Solitary bone lesion usually does not progress to multiple bone or visceral involvement, but a patient who presents with a single lesion must be thoroughly investigated to rule out multiple lesions. Treatment modalities of solitary bone lesions are, observation, curettage or intralesional steroid injection, as in this case. The mechanism of action of intralesional injection of corticosteroids has not been defined, but a recent study of thirty-nine patients with solitary eosinophilic granuloma showed that the use of percutaneous needle biopsy for the diagnosis and the treatment with intralesional administration of methylprednisolone relieved pain effectively, enabled the patient to avoid an operative procedure and resulted in osseous healing in 97%of the patients.

Differential Diagnosis List

Final Diagnosis

Solitary eosinophilic granuloma of radius

URL:	https://www.eurorad.org/case/1104
DOI:	10.1594/EURORAD/CASE.1104
ISSN:	1563-4086