Onion Skin Periosteal Reaction — ORE Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

HardRadiology & ImagingOnion Skin Periosteal ReactionORE Part 1

A 12-year-old presents with a 6-week history of slowly increasing, firm swelling over the left mandibular body. The lower left first permanent molar is extensively carious and non-vital, with a periapical radiolucency. An occlusal radiograph shows several parallel layers of new periosteal bone along the buccal cortex, producing an 'onion-skin' appearance. What is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Chronic osteomyelitis with proliferative periostitis

The best answer is **A: chronic osteomyelitis with proliferative periostitis** (periostitis ossificans/Garrè osteomyelitis). This classically affects younger patients and is associated with a low-grade odontogenic infection, often from a carious mandibular first molar with periapical disease. The periosteum lays down successive layers of new bone, giving the laminated onion-skin appearance. Osteosarcoma can produce periosteal new bone and must remain in the wider differential for atypical or progressive lesions, but it is not the most likely diagnosis in this tightly specified odontogenic presentation. Fibrous dysplasia usually has a ground-glass internal pattern rather than layered periosteal bone. Paget disease is generally a disease of older adults with diffuse mixed radiographic changes. A normal variant cannot explain new periosteal bone, swelling, and a non-vital infected tooth.

Reference: Kawai T, Hiranuma H, Kishino M, et al. Gross periostitis ossificans in mandibular osteomyelitis: review of the English literature and radiographic variation. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology. 1998. https://pubmed.ncbi.nlm.nih.gov/9768431/