Complete resolution and remodeling of chronic recurrent multifocal osteomyelitis on MRI and radiographs.

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare condition thought to be under-diagnosed, with a true prevalence of more than the 1 in 10,000 estimated. It is a condition that is classically described as polyostotic with a relapsing and remitting course, preferentially affecting the metaphyses of tubular bones in the pediatric population. Lesions have characteristic appearances of cortical hyperostosis and mixed lytic/sclerotic medullary appearances radiographically, with active osteitis and periostitis best seen with fluid-sensitive sequences on magnetic resonance imaging (MRI). There are reports of lesions resolving on follow-up radiographs and MRI scans, but no supporting images. In particular, although the marrow appearances and degree of osteitis have been shown to improve on MRI, complete resolution and remodeling back to normal has never been demonstrated. We present a case of a lesion that has completely healed and remodeled back to normal appearances on both radiographs and MRI, and consider this the standard for the often loosely used terms "normalization" and "resolution". We discuss the implications of this for our understanding of the natural history of CRMO, and how this adds weight to the condition being significantly under-diagnosed. It provides a "gold standard" to be aimed for when assessing treatments for CRMO, and the optimal outcomes that are possible. It also provides further insight into the potential of pediatric bone to recover and remodel when affected by inflammatory conditions.