Pycnodysostosis is an autosomal recessive, pan-ethnic bone disorder caused by pathogenic variants in the gene CTSK. Clinical features of pycnodysostosis include bones that are prone to fractures, even with minimal trauma. The fontanel, or soft spot, of the skull does not close and harden. Patients may have scoliosis and other misshapen bones, and have a short stature in adulthood. They may also have characteristic facial features and teeth that come in later than usual, or not at all. Intelligence and lifespan is not affected. To date, no genotype-phenotype correlation is known.
For information about carrier frequency and residual risk, please see the residual risk table.