• Definition: an inherited, diffuse bone disease that results in sclerotic thickening of the skeleton on radiological examination
• Etiology: infancy or early childhood
• Pathophysiology: gene mutations → inability of osteoclasts to generate acidic environment in the bone matrix → bone resorption with preserved osteoblastic function → overgrowth of bone with pathological bone composition
• Clinical features
  • Recurring pathological fractures (osteopetrotic bone tissue is very dense but brittle)
  • Cranial nerve disorders (e.g., palsies) due to hyperostosis and stenosis of the cranial nerve foramina
  • Pancytopenia due to reduced marrow space
  • Hepatosplenomegaly due to extramedullary hematopoiesis
• Diagnostics
  • X-ray: symmetrical, homogenous, sclerotic thickening of both cortical and trabecular bone (stone bone)
  • Calcium levels may be normal or low (especially in severe form, e.g., type I osteopetrosis).
• Therapy
  • Bone marrow transplant (potentially curative treatment): Functional osteoclasts may develop from unimpaired monocytes deriving from transplanted stem cells.