What is Cherubism?
Cherubism is a rare painless condition involving the bones of the face. The solid bone in the lower part of the skull and jaw (maxilla and mandible) is replaced by fibrous tissue that is less dense, leading to swollen looking cheeks. In some cases, the enlargement of the floor of the orbit (the bones surrounding the eye socket) causes the eyeball to tip upward. The name of the condition is derived from cherub (angelic looking, as depicted in Renaissance paintings).
The medical community currently believes that the condition develops when a gene that governs the function of cells that buildup bone (osteoblasts) and breakdown bone (osteoclasts) works in an atypical manner. Usually osteoblasts and osteoclasts build up and breakdown bone in a balanced way, so that the strength of bone is maintained. Persons with the genetic make up of cherubism appear to breakdown bone at an increased rate and to build it up in an atypical way (through large multinucleated cells). The imbalanced osteoblast and osteoclast activity appears to lead to the formation of fibrous tissue, which appears as bubbles or "spongy" in radiographs. The lesions of cherubism are graded into levels indicating the involvement of the mandible and/or maxilla, the resorption of the roots of teeth, and the involvement of the orbits.
Cherubism is usually first detected in early childhood. Symptoms of cherubism can spontaneously resolve themselves (regress). Regression may occur as early as puberty or as late as the 30's or 40's. Common clinical features of cherubism include:
- Bilateral swelling of the jaw (on both sides in the same area, although not necessarily to the same degree)
- More common in mandible than maxilla
- Upturned eyes (rim of sclera - the white of the eye - visible beneath the iris)
- Inverted V-shaped palate arches (the curved rear portion of the roof of the mouth)
- Enlarged submandibular lymphnodes
- Premature loss of primary teeth
- Failure of permanent teeth to erupt or random distribution on eruption.
- Rapid development in childhood, slowing during puberty, later stabilization with possible regression.
- Sometimes, cherubism is associated with Noonan syndrome, which includes a typical facial appearance with low set ears, sunken chest, low platlets, generalized mild low bone density, and subtle (usually) heart malformations.
Diagnosis of cherubism is usually based on the above symptoms through a physical examination, family history, and imaging (panoramic X-rays and CT scans). Biopsies can be conducted to establish the presence of cell patterns typical of cherubism in the lesions. It is presently believed that cherubism is histologically more like a giant cell granuloma than fibrous dysplasia, although the medical literature may still refer to cherubism as 'benign fibrous dysplasia of the jaws'.
About 200 cases of cherubism have been reported in medical publications. The medical community believes the condition is more common, although extremely rare. Cherubism has been documented internationally and among all races. Twice as many cases have been documented in boys/men as girls/women.
Genetic research conducted using the tissue of individuals in multi-generation families with members diagnosed with cherubism has led to the conclusion that some cases of cherubism may be attributed to mutations in the protein SH3BP2, which is coded for by a gene on the 4th chromosome. The pattern of inheritance in studied multi-generation families suggests that the gene is autosomal dominant. This means that a single affected parent can transmit the condition to their children and that, on average, 50% of their children will receive the gene. However, spontaneous cases do arise. The condition has a varied penetrance, meaning that symptoms of the condition can be different among individuals within the same family who carry the gene. In studied multi-generation families, scientists have found that all boys and men with the gene express it (display symptoms), while some (30-50% of) girls and women with the gene do not.
Cherubism presents several problems to affected individuals.
- Foremost, the facial appearance of those with cherubism appears atypical. Affected children can feel different, which is most negatively experienced through adolescence and the teens. Observers also may generalize the different appearance of the face of those with cherubism to cognitive deficits.
- The loss of teeth and misplacement of teeth can result in difficulty with eating.
- Cherubic lesions in the floor of the orbit can affect sight.
- Cherubic lesions in the back portion of the mandible can impede the motion of the jaw.
Treatment options depend on the symptoms.
- Children with cherubism should be monitored by their physician and their dentist. If lesions are in the orbits an ophthalmologist should also monitor the optic nerve.
- If the affected individual's appearance causes serious image problems, surgery can be performed to remove the fibrous tissue. However, the potential for spontaneous regression of the disease suggests that surgical interventions should be delayed until after puberty.
- Malplaced teeth that hinder chewing and or cause serious image problems can be adjusted through orthodontia or extracted.
- Missing teeth can be replaced with prostheses.
- Radiation is NEVER recommended!
- To date, there is no established medical intervention into the growth phase although several scientific investigations have been conducted.
- Parents of affected children need to ensure that they have an opportunity to talk about their feelings about the condition, especially during the teen years.
- Parents should educate caregivers and teachers about the disease to decrease the possibility of teasing.
Scientists continue to study cherubism, because understanding how bones are built up and break down has much wider medical value.
Ueki Y, Tiziani V,Santanna C, Maulik C, Garfinkle J, Ninomiya C, doAmaral C, Peters H, Habal M, Rhee-Morris L, Doss JB, Kreiborg S, Olsen BR, and Reichenberger E (2001) Mutations in the c-Abl-binding protein SH3BP2 cause excessive bone degradation in cherubism. Nature Genetics 28, 125-12
Tiziani V*, Reichenberger E*, Buzzo CS, Niazi S, Fukai N, Stiller M, Peters H, Salzano FM, Raposo do Amaral CM, and Olsen BR (1999) The gene for cherubism maps to chromosome 4p16. Am J Hum Genet 65(1):158-166