Sequential MR Images and Radiographs of Epiphyseal Osteomyelitis in the Distal Femur of an Infant

Magnetic resonance imaging (MRI) plays an important role in the diagnosis of osteomyelitis, especially during the early phase of the disease. The findings of sequential MRIs during the course of treatment in acute osteomyelitis in children have not yet been reported in the literature. We present a case of acute epiphyseal osteomyelitis in the distal femur of an infant. We monitored imaging changes by sequential MRIs and radiographs. MRI was more useful than radiograph for early diagnosis and evaluation of therapeutic response. 1. Introduction Acute hematogenous osteomyelitis in young children occurs mostly in the metaphysis or the diaphysis of a long bone. Acute hematogenous epiphyseal osteomyelitis is very rare with only a few cases having been reported [1–4]. Early diagnosis and appropriate treatment are important for acute epiphyseal osteomyelitis, because delays can allow the condition to spread from the epiphysis into the metaphysis or the knee joint [2, 4]. This may lead to sequelae of growth plate injury or articular cartilage destruction [1]. Magnetic resonance imaging (MRI) plays an important role in the diagnosis of osteomyelitis, especially during the early phase of the disease. MRI is also useful in evaluating soft tissue involvement, discerning both bone and soft tissue abscesses and showing coexisting articular abnormalities such as effusion or synovitis. The findings of sequential MRIs during the course of treatment in acute osteomyelitis in children have not yet been reported in the literature. In the current patient, we were able to evaluate sequential MRIs during the course of treatment for acute epiphyseal osteomyelitis and find the discrepancy among MR images, clinical findings, and plain radiographs. 2. Case Presentation A 26-month-old boy was referred to our department with a 10-day history of limping gait due to pain in his right leg. Physical examination and radiographs did not show any findings in the right leg. Two days later, he was admitted to our hospital again with pyrexia. Moreover, local heat and motion pain in the right knee were observed. He repeatedly had infections including sepsis and meningitis after birth because of a primary immunodeficiency disease. His mother had a selective immunoglobulin M (IgM) deficiency. Laboratory examinations on admission showed an elevated white blood cells (WBC) count of 18,900/μL with a left shift and a C-reactive protein (CRP) value of 5.75？μg/mL. Evaluation of immunoglobulin revealed significantly lower serum IgM level (14？mg/dL) and IgG level (657？mg/dL), along with normal IgA