Pycnodysostosis is a rare disorder that makes bones denser than usual, and people with this condition are often shorter than average.
Individuals may have bone deformities like a curved spine, a different-shaped collarbone, and delayed closure of skull plates. Their finger bones can also be shorter, and their bones, while dense, are brittle and break easily, especially in the legs, feet, jaws, and collarbones. People with pycnodysostosis may have distinct facial features like a prominent nose, forehead, and eyes, along with a small jaw. Sometimes, the whites of their eyes may have a blue tint. Children with this condition might have late-growing, irregular, or missing teeth that are prone to cavities. There’s no cure for pycnodysostosis, and since it’s so rare, treatments are personalized.
Pycnodysostosis is caused by pathogenic (disease-causing) variants in the CTSK gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background.