Garré Osteomyelitis

Garré osteomyelitis is a chronic non-suppurative osteomyelitis with proliferative periostitis, in which new bone forms in layers on the outer cortex in response to low grade infection. It is also called chronic osteomyelitis with proliferative periostitis.

It affects children and adolescents, mainly under 20 years, with no sex preference, and most often involves the posterior mandible next to a carious first permanent molar. It is rare in adults.

Pathophysiology. A low grade infection, usually from a carious pulp or periapical lesion, spreads through the cortex and stimulates the periosteum to lay down layers of bone, giving the concentric appearance.

The host response is strong and the organism is of low virulence, so abscess and sequestrum formation are minimal. After the source is removed the bone remodels.

A firm, bony, painless or mildly painful swelling of the lower face over the mandible, in a child with a carious or abscessed molar. Fever is mild or absent. The skin and mucosa are normal, and trismus is uncommon.

Rapid growth, pain at night, systemic features or neurological signs suggest another diagnosis such as sarcoma or Ewing tumour.

• Occlusal and panoramic radiographs: the classic onion skin appearance of one or more concentric layers of new bone along the outer cortex, with a radiolucent focus at the source tooth.
• CT shows the layering of bone and cortex integrity, and MRI is used when a tumour is suspected.
• Bloods: full blood count, C-reactive protein and ESR (often normal or mildly raised).
• Biopsy when the picture is atypical, when the swelling persists after the source is removed, or when features are worrying: reactive woven bone with chronic inflammation, with no tumour cells.
• Culture is rarely helpful.

Differential diagnosis.

• Ewing sarcoma and osteosarcoma
• Langerhans cell histiocytosis
• Fibrous dysplasia
• Caffey disease (infantile cortical hyperostosis)
• Chronic suppurative osteomyelitis
• Chronic recurrent multifocal osteomyelitis
• Leukaemia and metastatic neuroblastoma

• Remove the source: extraction of the carious tooth, or root canal treatment when the tooth is restorable. This is the key step and in most children it is curative.
• Antibiotics for 1 to 4 weeks, directed by clinical response: amoxicillin 250 mg orally three times daily at age 1 to 4 years, 500 mg three times daily at age 5 years and over, with metronidazole 7.5 mg/kg (maximum 400 mg) three times daily when infection is severe, or clarithromycin in penicillin allergy at weight based doses. Reduce amoxicillin when eGFR is under 30.
• The bone remodels and the swelling usually resolves over 6 to 12 months, and contour surgery is only needed for persistent deformity.
• Analgesia: paracetamol 15 mg/kg every 4 to 6 hours (maximum 75 mg/kg daily) with ibuprofen 5 to 10 mg/kg every 6 to 8 hours, avoided in dehydration.

Monitoring. Radiographs at 3, 6 and 12 months to confirm remodelling. Persistent growth or no regression after source removal needs biopsy.

Referral and escalation. Refer to paediatric dentistry or oral and maxillofacial surgery. Urgent referral for rapid growth, pain, systemic symptoms, or radiographs showing a sunburst pattern or a soft tissue mass.