Osteopetrosis

  • Associated with Avian Leukosis virus
  • Variable eosinophilic trabeculae that extend from and efface the normal cortex
  • Trabeculae lined by osteoblasts; rare osteoclasts
  • Reversal lines (basophilic lines following the contour of the trabeculae) are common
  • Frequent lacunae with osteoblasts
  • Intertrabecular space filled with loose fibrovascular stroma (NOT marrow)
12 week old chicken. Cortex and thickened and normal surface is obscured by dense trabeculae
12 week old chicken. Thick trabeculae with reversal lines, frequent lacunae, and fibrovascular stroma

May see irregular to ovoid, basophilic, intracytoplasmic inclusions stacked within myocardial cells

Same 12 week old chicken. Several myocardial cells contain irregular to oval, basophilic, intracytoplasmic inclusion (arrows). There is no associated degeneration.