An inherited disorder characterized by an increase in bone density; in severe forms the bone marrow cavity may be obliterated WordNet 3.0 & Open English WordNet

Osteopetrosis, literally "stone bone", also known as marble bone disease or Albers-Schönberg disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosis, in which the bones become less dense and more brittle, or osteomalacia, in which the bones soften. Wikipedia

An extremely rare inherited disorder whereby the bones harden, becoming denser, sometimes causing bones to dissolve and break, caused by malfunctioning osteoclasts’ inability to resorb bone Wikidata

A rare hereditary disorder characterized by hard, dense bones. Wiktionary

Hereditary disorder. Wiktionary (translation)