Caseous granuloma: tuberculosis or chronic recurrent multifocal osteomyelitis?

Area of Science:

• Pediatric rheumatology
• Autoinflammatory bone disorders
• Osteomyelitis research

Background:

• Chronic recurrent multifocal osteomyelitis (CREMO) is an autoinflammatory bone disorder stemming from innate immune system dysfunction.
• While typically characterized by sterile bone lesions, CREMO has not been previously associated with caseous granulomas.

Observation:

• A four-year-old boy presented with wrist pain, malaise, and pustulosis, later developing elbow pain and effusion.
• Histopathology revealed granulomatous osteomyelitis with caseating necrosis, and mycobacterial tests were negative.
• The patient was diagnosed with CREMO based on recurrent exacerbations, negative cultures, and characteristic histopathology and radiographic findings.

Findings:

• Treatment with naproxen and pamidronate resulted in complete symptom resolution.
• Radiographic evidence showed the disappearance of osteolytic lesions and periosteal reactions following treatment.
• This case represents the first documented instance of caseous granulomas in a patient diagnosed with CREMO.

Implications:

• Clinicians should consider CREMO in patients presenting with lytic bone lesions.
• The potential for caseating granulomas should be recognized in the differential diagnosis of suspected CREMO cases.
• This finding expands the histopathological spectrum of CREMO and may influence diagnostic and treatment strategies.