Chronic Recurrent Multifocal Osteomyelitis: A Case Report with Atypical Presentation

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory condition. The clinical picture consists of sterile osteomyelitis, typically with multiple-site lesions in the metaphysis of long bones and not uncommonly, symmetrical bone involvement. It is a poorly understood entity, whose prognosis, etiology and ideal treatment are still controversial. The authors report a case of unifocal presentation with an atypical location.

A previously healthy 12-year-old Caucasian girl came to our institution due to progressive pain on her left thigh for the previous 3 months. The initial X-ray showed a permeative, diaphyseal lesion of her left femur, with marked periosteal reaction. The differential initially included Ewing's sarcoma, osteosarcoma, subacute osteomyelitis, and Langerhans cell histiocytosis. Needle and open biopsies demonstrated the presence of chronic inflammatory infiltrate, with fibrosis, but no signs of neoplastic disease. Serologic and microbiological studies failed to demonstrate an infectious etiology. The patient was treated with nonsteroid anti-inflammatories, corticosteroids, and bisphosphonates for 6 months. Although no antibiotics were employed, the patient showed clinical and radiological improvement, at 18-month follow-up.

CRMO is a rare condition, and the absence of specific features constitutes a diagnostic challenge. A high level of suspicion is paramount to avoid unnecessary biopsies and repeated antibiotic regimens. Unifocal presentation of this disease, atypical locations, and absence of recurrence have all been previously reported, with the evidence pointing to a shared etiological process with no distinction being made between these variants. For this reason, the authors believe that the term "nonbacterial osteomyelitis" might be a more all-embracing designation.