Popliteal pseudoaneurysm caused by Nora's lesion of the femur in a young child: a rare presentation and first report.

Bizarre parosteal osteochondromatous proliferation (BPOP), or Nora's lesion, was first described by Nora et al. in 1983 as a rare, tumor-like lesion involving the bones of the hands and feet. Popliteal artery pseudoaneursyms in the pediatric population are also unusual. Here, we present a case of a young male with a popliteal artery pseudoaneurysm and distal femur lesion originally thought to be an osteochondroma. A 10-year old, Caucasian male was referred to our facility following an MRI concerning for a popliteal artery pseudoaneurysm. On physical exam, there was a palpable 5 × 5-cm pulsatile mass in the upper popliteal fossa with a normal pulse exam bilaterally. A computed tomographic angiogram demonstrated a 4.5-cm by 1.8-cm by 3.6-cm pseudoaneurysm adherent to a 3.5-cm thick, exostotic lesion of the posterior right femur. He was taken to the operating room for repair of the popliteal pseudoaneurysm and resection of his bone lesion. The final pathology was consistent with a popliteal pseudoaneurysm, osteochondroma, and bizarre parosteal osteochondromatous proliferation (BPOP), otherwise known as Nora's lesion. The location of the lesion and the age of our patient were both atypical for BPOP and to our knowledge, this represents the first report of a resulting popliteal artery pseudoaneurysm.