[Pelvic type of chronic recurrent multifocal osteomyelitis]

Area of Science:

• Pediatric rheumatology
• Orthopedic surgery
• Radiology
• Pathology

Background:

• Chronic recurrent multifocal osteomyelitis (CRMO) is a rare inflammatory bone disease affecting children and adolescents.
• Pelvic CRMO, particularly in the acetabular region, can present with hip joint effusion, mimicking other conditions.
• The condition is often associated with the Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis (SAPHO) syndrome.

Purpose of the Study:

• To describe the clinical and radiological features of juvenile and adolescent pelvic CRMO.
• To elucidate the natural history and potential therapeutic options for pelvic CRMO.
• To clarify the relationship between CRMO and SAPHO syndrome.

Main Methods:

• Retrospective analysis of 7 girls and 4 boys diagnosed with pelvic CRMO.
• Clinical evaluation including assessment of hip joint involvement.
• Radiological assessment using Tc99m-bone scan and MRI to characterize bone lesions and effusion.
• Histopathological review to identify the underlying "plasma-cell-sclerotic process".

Main Results:

• Pelvic CRMO manifested as solitary to multiple lesions (average 3) in the acetabular/paraacetabular regions.
• Tc99m-bone scan effectively delineated the extent of bone involvement.
• Three stages of osteomyelitis were observed, progressing to a Garrè-type sclerosing end-stage, potentially healing spontaneously.
• Concomitant hip joint effusion ("sympathetic coxitis") was common but reversible.
• Pain associated with CRMO showed a significant positive response to azithromycin therapy.

Conclusions:

• Pelvic CRMO is a distinct entity within the spectrum of SAPHO syndrome, not a diagnosis in itself.
• "Sympathetic coxitis" is a key clinical feature that requires recognition by pediatric rheumatologists and orthopedic surgeons.
• Azithromycin demonstrates promising therapeutic potential for managing CRMO symptoms, particularly pain.