Can Q fever cause spinal osteomyelitis?

Q Fever and Spinal Osteomyelitis

Yes, Q fever can cause spinal osteomyelitis, particularly in chronic Q fever infections. 1, 2 This manifestation is an important consideration in patients with vertebral osteomyelitis of unclear etiology, especially in endemic areas or those with risk factors for Q fever.

Epidemiology and Risk Factors

• Spinal osteomyelitis due to Q fever is relatively rare but likely underdiagnosed due to its insidious presentation and the need for specific testing 2, 3
• Most cases of Q fever vertebral osteomyelitis occur in adults, particularly males (88%), with a mean age of 67.2 years 2
• Adjacent aortic involvement is common (68% of cases), especially in patients with aortic grafts or aneurysms 2, 4
• In children, chronic Q fever more commonly manifests as chronic relapsing or multifocal osteomyelitis compared to adults 1, 5

Clinical Presentation

• The clinical presentation of Q fever vertebral osteomyelitis is typically insidious 2, 6
• Fever is frequently absent, making diagnosis challenging 2
• Patients may experience:
  • Back pain
  • Leg weakness
  • Asthenia (general weakness)
  • Delayed diagnosis is common, often months to years after symptom onset 2, 3

Pathophysiology

• Q fever vertebral osteomyelitis can occur through:
  • Direct extension from adjacent vascular infection (most common in adults) 2, 4
  • Hematogenous spread during bacteremic phase 3
• Histologically, the infection presents as granulomatous osteomyelitis with epithelioid and gigantocellular infiltrates and necrosis 3, 6

Diagnosis

• Diagnosis requires a high index of suspicion, especially in:
  • Culture-negative vertebral osteomyelitis 3, 6
  • Patients with aortic grafts or aneurysms 2, 4
  • Endemic areas for Q fever 2
• Diagnostic methods include:
  • Serology: High antibody titers to C. burnetii antigens (phase I IgG ≥800) indicate chronic Q fever 3
  • PCR of bone biopsy specimens can detect C. burnetii DNA 3, 6
  • Histopathology showing granulomatous inflammation (similar to tuberculosis) 3, 6
• Imaging techniques useful for diagnosis include:
  • CT, MRI, or duplex ultrasound 1
  • FDG-PET/CT has high sensitivity for low-grade vascular infections and can visualize other infectious foci 1

Treatment

• Treatment typically consists of:
  • Prolonged antimicrobial therapy, most commonly doxycycline and hydroxychloroquine combination for 18 months or longer 2, 3
  • Surgical management may be necessary for associated vascular infections 2, 4
• Response to treatment is variable, with limited long-term follow-up data in most cases 2

Special Considerations

• In children, Q fever osteomyelitis often presents as a chronic, relapsing, multifocal disease affecting multiple bones before diagnosis 1, 5
• Immunocompromised patients or those with underlying heart valve disease may be at higher risk for chronic Q fever, including bone manifestations 1
• Q fever should be included in the differential diagnosis of culture-negative granulomatous osteomyelitis, particularly when conventional antimicrobial therapy fails 3, 6

Pitfalls and Caveats

• Delayed diagnosis is common due to the insidious nature of symptoms and lack of specific clinical features 2, 6
• Q fever osteomyelitis may be misdiagnosed as tuberculosis due to similar histological findings (granulomatous inflammation) 3, 6
• Standard bone cultures will be negative, requiring specific testing for C. burnetii 3
• Consider Q fever in cases of culture-negative vertebral osteomyelitis, especially in patients with vascular grafts or aneurysms 2, 4