Figure 10b. Langerhans cell histiocytosis in a 6-year-old boy who presented with lower back pain. (a) Fast SE STIR whole-body MR image demonstrates increased marrow signal intensity in the collapsed vertebral body L5 (vertebra plana) without an associated soft-tissue mass (arrow). No further bone involvement was seen. (b) T2-weighted fat-saturated sagittal image does not show any spinal stenosis. (c) Posterior view from bone scintigraphy demonstrates bilateral increased activity at the level of L5 (arrow), a finding that initially suggested spondylolysis or spondylolisthesis. (d) Three-dimensional surface-shaded CT image shows the degree of collapse of the L5 vertebral body.