Lysosomal storage disease is a collective term for the various metabolic disorders due to defects in lysosomal function resulting in an abnormal accumulation of toxic materials in the cell. One of them is pycnodysostosis. This condition is characterized by having a short stature and fragile bones. In males, the height of an adult with this disease is often less than 59 inches. Females with pycnodysostosis are generally shorter.
Pycnodysostosis is associated with genetic mutation located in chromosome 1q21. The defective gene affects the production of a cysteine protease, i.e. cathepsin K, in osteoclasts.
The condition is inherited in an autosomal recessive pattern. This means that the individual has two copies of the defective gene and therefore manifests symptoms associated with the disease. A carrier of the disease would have only one copy of the defective gene and therefore may not show symptoms. One of the distinctive symptoms of this disorder is osteoporosis. The bones are abnormally dense. There is also a tendency of certain bones, such as the distal phalanges and the collar bone, to go through slow progressive deterioration.