A muscular lesion suggestive of focal myositis in a child with Proteus syndrome

Proteus syndrome is a polymorphic hamartomatous disorder associated with a broad spectrum of rare congenital malformations. Many neoplasms have been linked to this condition, including lipomas, lymphangiomas, and hemangiomas. The authors describe a case of a congenital muscular lesion in a child with Proteus syndrome. This mass was painless but was growing out of proportion to her leg musculature. A magnetic resonance imaging scan and incisional biopsy showed findings consistent with focal myositis. The clinical, radiographic, and histologic characteristics of this previously undescribed lesion are discussed, with a brief review of the literature.