A patient presents with bilateral, symmetric jaw swelling that has been slowly enlarging over the past 2 years. The patient is a child, and the swelling is painless. What is the most likely diagnosis?

Cherubism is a rare autosomal dominant condition caused by mutations in the SH3BP2 gene, characterized by progressive, bilateral, symmetric enlargement of the jaw during childhood. The mandible (and sometimes maxilla) is replaced by fibrous tissue and giant cells, creating a classic angelic or 'cherub-like' facial appearance due to bilateral jaw fullness. The enlargement typically begins around age 2-4, progresses during childhood, and often stabilizes or partially regresses after puberty. Radiographically, multilocular radiolucencies are seen bilaterally. Fibrous dysplasia typically presents unilaterally and in older individuals. Paget's disease occurs in older adults. Mumps causes parotid (not jaw bone) enlargement with acute onset.