Diseased PSTPIP2-deficient mice are osteopenic and have erosive bone lesions that are associated with increased osteoclast numbers and activity. (A) Representative 3D reconstructions of trabecular areas of proximal tibias from PSTPIP2-deficient 3.5-month-old cmo and 3-month-old Lupo mice (right panels) and their corresponding WT control mice (left panels). (B) Quantitative micro-CT analyses of 3-month-old female mice showing that, compared with WT controls (white bars), PSTPIP2-deficient mice (black bars) have decreased proximal tibia bone volume to total volume (BV/TV). Figures in parentheses indicate the numbers of mice in each group. (C) Representative images of paws and proximal tails from cmo and WT control mice. Erosive bone lesions are seen on micro-CT reconstructions of paws and tails of diseased cmo mice. (D) Lumbar vertebrae from Lupo mice demonstrate osteopenia. (E) Increased TRAP staining in sections of femoral cortex of cmo compared with WT controls. Bottom panels are higher magnifications of the boxed regions in the top panels. (F) TRAP staining of tail vertebrae (top panels) and proximal femurs (bottom panels) of Lupo mice and WT controls. Arrows indicate TRAP⁺ osteoclasts. (G) Electron micrographs of vertebral osteoclasts. Arrows indicate the ruffled border.