Atypical, polyarticular lipoma arborescens in a child.

Introduction: Lipoma arborescens is a rare, tumor-like lesion commonly involving synovial joints and less commonly bursae and synovial tendon sheaths. Case Outline: We report a case of a 12-year-old boy with symmetric involvement of the bicipitoradial bursae, synovial sheaths of extensor compartments of both hands and medial ankles. The diagnosis of polyarticular lipoma arborescens was proposed on magnetic resonance (MR) imaging and this diagnosis was histologically proven after biopsy of the bursae and later by open surgery of the synovial sheath of the right ankle tendons. Literature search was performed and twelve cases with polyarticular involvement were analyzed. Lipoma arborescens commonly involves suprapatellar recess of the knee and very rarely other joints or bursae. Histological analysis revealed an accompanying non-necrotizing granulomatous synovial inflammation. Conclusion: Polyarticular lipoma arborescens is a rare entity and symmetrical involvement of the joints other than the knees is exceedingly rare. MR imaging plays a significant role in the diagnostic protocol, and the characteristic fatty signal on MR imaging is highly suggestive of lipoma arborescens.