Pycnodysostosis

The pycnodysostosis ( OMIM: 265800 ) is an extremely rare bone disease from the shape of the circle Osteopetrosen. Since its first description in 1962, only a few hundred cases have been reported worldwide (as of 2006).

Clinical features

Affected patients there is a marked increase in bone mass, which shows up as compressed bone structure in the radiograph. These densified structure is less stable than normal bone and the patients often suffer from fractures. Other typical features are: short stature, deformities of the face skull, spondylolysis of the lumbar vertebral body and underdevelopment of the clavicle. The patients show a normal mental development. Unlike other Osteopetrosen find usually no anemia or brain nerve damage.

Genetic basis

The pycnodysostosis based on an autosomal recessive genetic mutation in chromosome 1 q21 locus, which leads to a sub- function of the protein cathepsin K. Without cathepsin K is the body's bone resorbing cells ( osteoclasts) can not break down the bone and it comes in the context of bone growth and remodeling in an accumulation of bone substance.

The French painter Henri de Toulouse- Lautrec suffered probably to pycnodysostosis.