Presentations

Abstract

Introduction:

A chief complaint of a new limp or refusal to bear weight in the pediatric population, especially in the toddler age group, can be challenging to diagnose. Infectious osteomyelitis, transient synovitis, rheumatologic conditions, and malignancy are major categories around which workup is focused. Here, we present a rare diagnosis of chronic non-bacterial osteomyelitis (CNO). CNO is a chronic, inflammatory bone disease with slightly over 500 reported cases worldwide. CNO affects children and adolescents, typically females, with a peak incidence between 7-12 years of age. Once thought of having a post-infectious origin, CNO is no longer considered as such after extensive microbiological analyses failed to show pathogenic involvement and lack of response with antibiotic use. The current school of thought is that CNO is primarily an immunologic disorder where there is a cytokine imbalance. The disease can be persistent or episodic in symptomology and can affect one or multiple bones. We present a case of a 2-year-old female with the ultimate diagnosis of CNO, and the extensive workup associated with such a rare disease.

Case Description:

A previously healthy 2-year-old African American female initially presented with visible atraumatic right-sided limp leading to an emergency department visit. The limp first developed approximately one month after a bout of pneumonia. The initial diagnosis was presumed transient synovitis. Two weeks following emergency department discharge, the limp progressed to involve bilateral lower extremities with refusal to bear weight. At her orthopedic follow-up, she was noted to have subtle ataxia and unsteady knees bilaterally. Given the progression and duration of symptoms, she was admitted for evaluation of limp with MRI pelvis. Through the hospital course, she complained of low back pain with tenderness to palpation of lower right back along the SI joints. She was unable to bear weight or walk. She was started on scheduled Naproxen with some improvement. She had extensive workup with multiple sub-specialties including orthopedics, infectious disease, neurology, hematology/oncology, and rheumatology. She also had extensive diagnostic testing with magnetic resonance imaging (MRI) of the pelvis, x-ray of the hips, computed tomography of the head, ultrasound of the abdomen, and bone marrow biopsy. The biopsy showed several areas of fibrosis of cortical bone but no malignancy. With these results, hematology was concerned for CNO. Whole-body MRI revealed increased short inversion time inversion recovery (STIR) signal bone marrow in multiple locations consistent with CNO. Gait improved in 24 hours after initiating treatment with steroids, Cellcept, and Plaquenil.

Discussion:

Limping in a young child can have a variety of etiologies. It often involves multiple subspeciality consults with a vast array of diagnostic testing. Though CNO tends to have a peak incidence in 7-12-year age group, it should be considered in all age groups. Whole-body MRI is the gold standard imaging modality for diagnosis of CNO. Bone biopsy is confirmatory. As this is a diagnosis of exclusion, it is important to rule out other disorders such as infectious cases, cerebellar abnormalities, intra-articular processes, and malignancies as in this case. Another important diagnosis to consider in this clinical scenario is scurvy, as MRI findings are identical. This patient was growing well along her growth curve and did not show any other associated symptoms. Additionally, her bone marrow biopsy showed fibrotic changes, which is pathognomonic for CNO.

Conclusion:

Though CNO remains a rare diagnosis of exclusion, with its spectrum of severity, it is important to keep this differential diagnosis in mind when managing a pediatric patient with atraumatic, insidious onset of limp with refusal to bear weight.