Metabolic defect: cathepsin k deficiency

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Cathepsin k is responsible for bone reabsorption (or resorption) in normal bone cells (osteoclasts). A deficiency of the enzyme hampers adequate resorption in the organic matrix, a process essential for normal bone maintenance.

Micrognathia (small jaws)	Enlarged Frontal Occipital

Inadequate resorption causes bones to be abnormally dense and brittle. Presenting abnormalities often include short stature, dense brittle bones, short fingers, and the wide open soft spot of the skull. Bone fractures are also a big problem for patients. Other abnormalities involve the head and face, teeth, collarbones, skin, and nails. The front and back of the head are prominent.

Short stature (adult height less than 150 cm)

Craniofacial abnormalities

Delayed, altered dentition

Aplasia of clavicle

Increased bone density

Hypoplasia of clavicle

Osteosclerosis, generalized

Susceptibility to fracture

Scoliosis

Spondylolysis, Spondylolisthesis

Narrow ilia

Brachydactyly

Acro-osteolysis of distal phalanges

Osteomyclitis

Wrinkled skin over dorsa of fingers

Grooved nails

Flattened nails

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1. Medicinenet. www.medicinenet.com/script/main/Art.asp?li=MNI&ArticleKey=462&page=3 Accessed July 2004.

2. Medicinenet. www.medicinenet.com/script/main/Art.asp?li=MNI&ArticleKey=462&page=2 Accessed July 2004.

3. National Center for Biotechnology Information; OMIM(TM), Online Mendelian Inheritance in Man. www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=265800 Accessed July 2004.

4. Bruce D. Gelb, Dieter Brömme, Robert J. Desnick. „Pycnodysostosis: Cathepsin K Deficiency.” The Metabolic and Molecular Bases of Inherited Disease, 8th Edition Online. McGraw-Hill. http://genetics.accessmedicine.com/server-java/Arknoid/amed/mmbid/co_chapters/ch137/ch137_p01.html Accessed September 2004.