Osteopetrosis

**Semantic type:** Congenital Abnormality|Disease or Syndrome

**Definition:** A rare genetic disorder inherited in an autosomal dominant, autosomal recessive, or X-linked recessive pattern. In the majority of cases it is caused by mutations in the CLCN7, TCIRG1, or IKBKG genes. It is characterized by excessive bone formation due to the failure of osteoclasts to resorb bone. It manifests with deformities, fractures, hepatosplenomegaly, anemia, and extramedullary hematopoiesis.