P3.243: Case Report: Peculiar Pediatric Medial Clavicle Swelling

Introduction: A 9-year-old male patient presents with swelling of the left medial clavicle which has been present for two months. The swelling has become increasingly painful and has doubled in size in the last week. He was initially seen by his pediatrician and now presents as a referral to pediatric sports medicine.

Case Description: The patient denies fevers and there has been no injury. The exam was notable for a firm mass along the medial clavicle with no overlying erythema and left-sided cervical and submental lymphadenopathy. Initial x-rays of the clavicle showed a lytic lesion of the medial clavicle. MRI showed an expansile lesion measuring approximately 4.9cm. The lesion had some intrinsic T1 hyperintensity, but overall heterogeneous contrast enhancement. There was also abnormal bone marrow signal of the T5 vertebrae. Lab work revealed normal CBC and inflammatory markers. He was urgently referred to an orthopedic surgeon specializing in bone lesions. A biopsy was performed with pathology consistent with osteomyelitis, immunohistochemistry testing was negative, and the bacterial culture of the lesion was negative. A referral was made to pediatric infectious disease and rheumatology. He was ultimately diagnosed with chronic recurrent multifocal osteomyelitis (CRMO) with spinal involvement which is considered severe given the risk for vertebral compression fracture. A whole-body MRI to rule out additional lesions was recommended. He was started on multimodal treatment including naproxen, methotrexate, a tumor necrosis factor (TNF)-alpha inhibitor, and a bisphosphonate.

Discussion: Clavicular lesions in children are relatively uncommon, however when diagnosed require a multi-disciplinary team. The differential diagnosis for a pediatric medial clavicular lesion is broad including CRMO, infectious osteomyelitis, stress fracture, sternoclavicular dislocation, Langerhans’ cell histiocytosis, malignancy (Ewing sarcoma, osteosarcoma, metastatic bone lesion), bone cyst, and enchondromatosis. Initial imaging recommendations include an x-ray and MRI if there are x-ray findings such as a lytic expansile lesion. Initial laboratory workup includes a CBC, ESR, and CRP. Final diagnosis of a medial clavicular lesion often requires a biopsy. Return to play is variable and depends on response to treatment. Patients who have not responded to treatment after 3 months or patients with spinal involvement require monitoring every 3 months for at least a year. Early data suggests most patients go into remission within one year of diagnosis, however, there has been a high percentage of patients who later develop disease flares.

Conclusion: CRMO is a rare auto-inflammatory bone disorder typically affecting children between the age of 7 and 9 years. Common sites affected include the metaphysis of lower extremity long bones, vertebrae, mandible, clavicle, and pelvis. It is critically important to promptly diagnose and start treatment to prevent complications. This case highlights keeping a broad differential for bone lesions and the importance of timely engagement with other pediatric subspecialists.