What Your Test Results Mean:

Carriers typically show no symptoms of pycnodyostosis; however, carriers are at an increased risk of having a child with pycnodysostosis. Risk for current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

Pycnodysostosis is an inherited lysosomal disorder caused by deficient levels of the lysosomal enzyme cathepsin K. Decreased cathepsin K leads to multiple bones issues in the individual such as short stature and dense and brittle bones causing the individual to easily suffer from fractures. Delayed or abnormal development of the teeth is also seen with this disorder.

Treatment for pycnodysostosis involves managing the symptoms. Growth hormone can help to improve the height of the individual, as well as surgery to correct deformities in the face and jaw. Dental care is important as well. Lifespan is not affected.

How the Genetics Works:

Pycnodysostosis is an autosomal recessive disorder caused by pathogenic variants in the Cathepsin K gene, CTSK. In general, individuals have two copies of the CTSK gene. Carriers of pycnodysostosis have a single variant in one copy of the CTSK gene while individuals with pycnodysostosis have variants in both copies, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.