Synchronous Lipoma arborescens of bilateral wrist: An extremely rare manifestation and a new perspective on etiopathogenesis.

Lipoma arborescens is a rare lesion wherein abnormal proliferation of adipocytes in the subsynovial region is seen. Whether it is neoplastic or not is still not entirely clear. Usually, Lipoma arborescens is seen unilaterally around knee joint but it can also be seen around tendon sheaths or bursa in adults. Multiple lesions are also reported. Involvement of wrist is extremely rare. We are presenting a case with bilateral wrist involvement by Lipoma arborescens which to the best of our knowledge is first one in English literature. There are a host of co-morbid/associated conditions reported with Lipoma arborescens out of which chronic irritation and inflammation appears to be most significant. We are proposing a novel perspective on etiopathogenesis of Lipoma arborescens based on extant understanding of cellular differentiation and information gleaned from fetal autopsies. The new perspective also explains the predilection for knee joint.