Rare presentation of chronic recurrent multifocal osteomyelitis of the Iliac wing mimicking Ewing's sarcoma

Abstract

This report describes a case of chronic recurrent multifocal osteomyelitis (CRMO) in an 11-year-old girl, involving the iliac bone as an initial, solitary site. Atypical imaging features were suspicious of a bone tumour, such as Ewing's sarcoma. Chronic recurrent multifocal osteomyelitis is a great masquerader and can present atypically. Radiologists should be familiar with both typical and atypical presentations, to determine an accurate diagnosis and guide appropriate management. Timely diagnosis may avoid invasive bone biopsy and inappropriate long-term antibiotic prescription for children.

Keywords: CRMO; Chronic recurrent multifocal osteomyelitis; Ilium; MRI; rare.

FIGURE 1

An 11-year-old-girl with chronic recurrent multifocal osteomyelitis: Initial plain radiograph of the pelvis demonstrated diffuse sclerosis of the right iliac wing (arrows).

FIGURE 2

Magnetic resonance imaging of the pelvis performed without and with gadolinium: (a) Axial T2 fat-saturated image of the pelvis showing heterogeneous marrow signal within the right iliac wing with marrow expansion (red arrows). Diffuse layered periosteal reaction was noted with increased T2 signal in the adjacent part of the iliacus and gluteal muscles (yellow arrow). (b) Coronal short tau inversion recovery (STIR) image of the pelvis showing layers of periosteal reaction (yellow arrow). Increased marrow signal could be seen extending close to the acetabular roof but without intra-articular extension (red arrows). (c) Coronal fat-saturated image gadolinium enhanced T1 weighted image indicated mild sacroiliitis with post contrast enhancement (green arrow) and heterogeneous marrow enhancement (blue arrow). In addition, there was enhancement of the adjacent muscles.

FIGURE 3

Follow-up imaging with a radiograph of the pelvis and whole-body magnetic resonance imaging (MRI) performed 3 months after treatment: (a) Plain radiograph of the pelvis showing similar findings of sclerosis of right iliac wing. (b) Magnified fat-saturated T2 weighted coronal image on whole-body MRI shows significant improvement of the oedema and surrounding periosteal reaction (arrow). Note the absence of adjacent muscle inflammation. (c) Magnified section of the whole-body MRI, coronal T2 weighted fat-saturated MR image of the left lower leg showing increased marrow signal involving the inferior talus, cuboid (arrows) and base of 5th metatarsal bone (not shown). This involvement of multiple bones with regression of inflammation in the ilium after conservative treatment confirms the diagnosis of chronic recurrent multifocal osteomyelitis.