Nora's Lesion: Bizarre Parosteal Osteochondromatous Proliferation Causing Splay Foot Deformity: A Case Report.

Nora's lesion, or bizarre parosteal osteochondromatous proliferation (BPOP), is a rare benign lesion that is made up of varying degrees of cartilage, bone, and spindle cells. Most notably, calcification of the cartilage or "blue bone," is a feature of the disorder. The condition principally affects long tubular bones of the hands and feet, and is generally seen in patients in their second and third decades of life. We present a case of BPOP occurring in the second interspace with symptoms that would be consistent with a more common diagnosis of predislocation syndrome, or a second interspace neuroma. This case study may help the clinician in considering a more subtle cause of a splay deformity in the second interspace, and walk through the diagnostic and treatment course for BPOP.