However, about 10-15 percent of people that develop the disease without any family history also have a mutation in the SQSTM1 gene.Pagets disease of bone is associated with mutations in RANK. Receptor Activator of Nuclear Factor κ B (RANK), which is a type I membrane protein that is expressed on the surface of osteoclasts and is involved in their activation upon ligand binding. Additional genetic associations include:

Pathogenesis
The pathogenesis of Pagets disease is described in four stages:
Osteoclastic activity
Mixed osteoclastic – osteoblastic activity
Osteoblastic activity
Malignant degenerationInitially, there is a marked increase in the rate of bone resorption in localized areas, caused by large and numerous osteoclasts. These localized areas of pathological destruction of bone tissue (osteolysis) are seen radiologically as an advancing lytic wedge in long bones or the skull. When this occurs in the skull, it is called osteoporosis circumscripta. The osteolysis is followed by a compensatory increase in bone formation induced by the bone-forming cells, called osteoblasts, that are recruited to the area. This is associated with accelerated deposition of lamellar bone in a disorganized fashion. This intense cellular activity produces a chaotic picture of trabecular bone ("mosaic" pattern), rather than the normal linear lamellar pattern. The resorbed bone is replaced and the marrow spaces are filled by an excess of fibrous connective tissue with a marked increase in blood vessels, causing the bone to become hypervascular. The bone hypercellularity may then diminish, leaving a dense "pagetic bone," also known as burned-out Pagets disease.
Folliculitis nares perforans is characterized by small pustules near the tip of the inside of the nose, lesions that become crusted, and when the crust is removed it is found that the bulbous end of the affected vibrissa is embedded in the inspissated material. : 774

See also
Skin lesion


== References ==