A Rare Case of Neonatal Rib Osteomyelitis: Diagnostic Challenges and Successful Conservative Management

To the Editors: Rib osteomyelitis is an exceptionally rare form of neonatal osteomyelitis, with only a handful of cases reported in the literature. Its nonspecific presentation—low-grade fever, irritability or isolated chest wall swelling—combined with frequently inconclusive early laboratory and radiographic findings, poses a significant diagnostic challenge, often leading to misdiagnosis as soft-tissue infection, birth trauma or benign mass. Moreover, the rarity of this pathology limits the development of standardized management approaches.1–4 We report a term female neonate previously treated with whole-body therapeutic hypothermia for hypoxic–ischemic encephalopathy, discharged home on day of life 10 after an unremarkable early sepsis evaluation. She was readmitted on day 12 with low-grade fever (37.8°C), elevated C-reactive protein and procalcitonin, and neutrophilic leukocytosis. Full infectious evaluation was negative, including blood, urine, stool and cerebrospinal fluid cultures, and a nasopharyngeal respiratory virus panel. Empiric broad-spectrum intravenous antibiotic therapy with amikacin, vancomycin and cefotaxime was initiated. A right anterolateral chest wall swelling appeared during hospitalization (Fig. 1). Chest radiography was unremarkable. Point-of-care ultrasonography showed a well-defined hypoechoic subcostal collection, initially interpreted as an organizing hematoma with costal cartilage detachment. Contrast-enhanced magnetic resonance imaging (MRI) subsequently revealed a large multiloculated abscess with necrotic-liquefactive content involving the anterior arc of the right ninth rib, with cortical disruption, bone marrow edema, osteocartilaginous involvement and extensive perilesional soft-tissue inflammation. No pleural effusion or intrathoracic extension was identified. All microbiological studies, including a methicillin-resistant Staphylococcus aureus nasal swab, remained negative throughout the hospitalization. A comprehensive immunological evaluation showed immunoglobulin levels, lymphocyte subsets and complement fractions within age-appropriate limits.FIGURE 1.: Clinical photograph showing a right anterolateral chest wall swelling in the neonate. The lesion appears as a soft, poorly demarcated, mildly erythematous bulge without overlying skin breakdown. Subtle venous prominence is visible across the surface, consistent with the underlying mass effect.Following infectious disease consultation and in accordance with European Society for Paediatric Infectious Diseases recommendations, amikacin and cefotaxime were discontinued, while vancomycin and piperacillin–tazobactam were administered intravenously for a total of 4 weeks, then transitioned to oral clindamycin to complete a 6-week total course. No surgical drainage or debridement was required. Inflammatory markers normalized progressively, the chest wall swelling resolved and the infant was discharged after 33 days in good clinical condition. This case illustrates 3 important clinical points. First, sequential and escalating imaging is indispensable: plain radiographs were persistently normal despite significant osseous destruction, and ultrasonography was initially misleading—a pitfall already documented in prior reports.2–4 MRI remains the gold standard, as it defines the extent of intraosseous and soft-tissue involvement and, crucially, identifies or excludes intrathoracic complications that require surgical intervention.1–5 Second, culture negativity—occurring in up to one-third of neonatal osteomyelitis cases—should not defer diagnosis or adequate treatment when imaging is diagnostic.1 Third, even a large intraosseous abscess can be successfully resolved with prolonged antimicrobial therapy alone, provided respiratory function is preserved and intrathoracic extension is absent, consistent with the conservative outcomes reported in the few available neonatal rib osteomyelitis cases.2–5 This report contributes to the very limited literature on neonatal rib osteomyelitis and highlights the importance of high clinical suspicion, timely MRI, and tailored antimicrobial management to avoid diagnostic delay and optimize outcomes in this vulnerable population.