P CBD X Even the vaccinated can be vulnerable: spotting rare pneumococcal osteomyelitis early

 A

Here’s a structured way to approach this case:

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Case Summary

• Patient: 15-month-old girl

• Presentation: Acute refusal to bear weight on the right leg; inconsolable crying overnight.

• Relevant Background: Thriving, immunocompetent, up-to-date vaccinations including pneumococcal vaccines.

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Differential Diagnosis

In a toddler with acute onset refusal to bear weight:

1. Infectious Etiologies

   • Septic arthritis: Usually acute, very painful, may involve fever, joint swelling, limited range of motion.

   • Osteomyelitis: Often presents with localized pain, refusal to bear weight, sometimes mild fever; commonly affects long bones.

   • Transient synovitis: Typically post-viral, milder, less systemic illness, self-limited.

2. Trauma

   • Fracture (including occult fracture)

   • Toddler’s fracture (spiral fracture of tibia)

3. Inflammatory / Other

   • Malignancy (rare) – leukemia, bone tumors

   • Non-accidental injury (consider if history is unclear)

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Important Features in This Case

• Vaccinated against pneumococcus: Reduces risk of invasive pneumococcal disease but does not eliminate it, especially for non-vaccine serotypes.

• Immunocompetent: Suggests unusual infection is less likely but still possible.

• Acute refusal to walk: Strongly suggests musculoskeletal pathology.

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Investigations to Consider

1. Laboratory

   • CBC with differential (look for leukocytosis)

   • CRP and ESR (markers of inflammation)

   • Blood cultures (especially if osteomyelitis suspected)

2. Imaging

   • X-ray of the affected leg (initial, may be normal early in osteomyelitis)

   • Ultrasound if joint effusion suspected

   • MRI is the gold standard for detecting early osteomyelitis and differentiating from septic arthritis

3. Procedures

   • Joint aspiration if effusion present

   • Bone biopsy if diagnosis unclear

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Key Considerations

• Pneumococcal osteomyelitis in a vaccinated child is rare but can occur, often with non-vaccine serotypes.

• Early recognition is crucial to prevent complications such as bone destruction, chronic osteomyelitis, or sepsis.

• Empiric antibiotics should cover Staphylococcus aureus (including MRSA depending on prevalence) and potentially Streptococcus pneumoniae until cultures guide therapy.

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Management Principles

1. Hospital admission for IV antibiotics

2. Empiric coverage:

   • Nafcillin or oxacillin (or cefazolin) for MSSA

   • Vancomycin if MRSA prevalent

   • Consider ceftriaxone if pneumococcal coverage needed

3. Surgical consultation if abscess, necrotic bone, or failure to respond to antibiotics

4. Follow-up imaging to ensure resolution

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Summary

A previously healthy, fully vaccinated 15-month-old with acute refusal to bear weight is likely to have infectious osteoarticular pathology. Pneumococcal osteomyelitis, although rare in vaccinated immunocompetent children, remains a possibility. Prompt lab work, imaging, and empiric IV antibiotics are warranted, with early orthopedic consultation.

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If you want, I can draw a timeline of likely disease progression and diagnostic steps for this patient, which often helps in presentations or teaching. It would make the case much clearer visually. Do you want me to do that?