Eosinophilic Granuloma of the Pubis

Clinical History

49 year old gentleman presented with a short history of groin pain.

Imaging Findings

A 49 year old gentleman presented to our hospital with a 3 week history of left hip pain radiating to his groin. He reported no associated symptoms of note or relevant past medical history. Investigations revealed no signs of sepsis A provisional diagnosis of adductor tendonitis was made by the rheumatology team. An ultrasound scan revealed no abnormalities, and a steroid injection was performed in an attempt to alleviate his discomfort. This unfortunately provided no improvement of his symptoms. A subsequent MRI scan (Fig 1) demonstrated a lesion in the left pubic ramus. There was significant marrow oedema with high signal changes in the adjacent soft tissues indicating an inflammatory process. However these changes were non-specific. Therefore, a CT scan was performed which demonstrated a lytic lesion, in the left suprapubic ramus with subtle periosteal reaction (Fig 2a). There was also a small breach in the cortex (Fig 2b). These features suggested sub acute osteomyelitis as the most likely diagnosis. Radioisotope studies supported this as it revealed no associated lesions throughout the skeleton.Excision biopsy to confirm the diagnosis was performed. Histology revealed the presence of eosinophils, neutrophils and Langerhan-type cells (Fig 3) and adjacent reactive bony changes. Immunohistochemistry confirmed the presence of Langerhan type cells. These features are entirely consistent with eosinophilic granuloma (EG). Following discharge the patient has been seen in outpatient clinic and has made a full post-operative recovery with no residual pain.

Discussion

Eosinophilic granuloma is a disease of unknown aetiology. It is grouped with Hand-Schuller-Christian Disease and Letterer-Siwe syndrome under the term Langerhans Cell Histiocytosis (LCH). This condition is characterised by an abnormal proliferation of histiocytes in various parts of the reticuloendothelial system. The LCH cells differ from the normal Langerhan cells in that its development is arrested at an early stage¹. EG is primarily a disease of children and adolescents. Although the age range is wide (less than a year to 68 years), 80% present before the age of 10 years. Only 10% of the patients are more than 40 years ². Fifty to seventy percent are solitary lesions. The most common sites are skull followed by proximal femora, tibia, scapula, ribs, pelvis, vertebra and humerus. However, only 15% of the lesions occur in the pelvis with only 2% occurring in the pubis ³. Localised pain and tenderness are the most common symptoms. Radiographically, EG demonstrates varied appearances. Tubular bones may show a diaphyseal lesion with permeative destruction and periosteal reaction which may be subtle or overt, undulating and have a ‘onion skin’ appearance . This may mimic an aggressive lesion like Ewing ’s tumour or osteomyelitis in a child and a plasmacytoma or malignant deposit in adults. It can also present as a well defined lucency in the medulla with a thin sclerotic rim and endosteal scalloping. Flat bones tend to show a sharply marginated punched out lucent lesion resembling a benign process. In the skull, in children, geographic destruction of the bone with bevelling of the edges is a characteristic feature, but button sequestrum may occasionally be seen. Vertebra plana is a classic lesion of the spine where the vertebral body often collapses and is often wafer thin. The clinical course of solitary lesions is benign in most cases and treatment with curettage leads to complete healing⁴.

Differential Diagnosis List

Final Diagnosis

Eosinophilic granuloma in an adult.

URL:	https://www.eurorad.org/case/5364
DOI:	10.1594/EURORAD/CASE.5364
ISSN:	1563-4086