Fig 1. Clinical course of unusually severe BU in the index patient P1.

All four limbs were affected by edematous BU lesions, with osteomyelitis involving ten bones and septic arthritis involving two joints. (A) Severe edema of the right leg and foot and edema of the left foot (left panel) leading to amputation of the lower right leg (right panel). (B) Mediodiaphyseal lacuna of the lower third of the right tibia and major soft tissue enlargement (left panel). Hypercondensation of the proximal third of the left tibia and lacuna of the lower third of the fibular diaphysis with central sequestrum (right panel). (C) Intra-articular effusion of the right elbow associated to osteolysis and periostal reaction of the humerus, the olecranon and the radial head (left panel). Forearm diaphyseal lacuna of the left radius with sequestrum and partly consolidated fracture of the left radius (right panel).