Author: Dr Delwyn Dyall-Smith FACD, Dermatologist, 2010.
Hereditary gingival fibromatosis describes a group of rare genetic conditions in which the gums become enlarged, growing over the teeth. Hereditary gingival fibromatosis specifically occurs in the absence of other identifiable medical syndromes or medications known to cause gum overgrowth. It has also been called hereditary gingival overgrowth, idiopathic gingival overgrowth, elephantiasis gingiva, hypertrophied gingiva and hereditary gingival hyperplasia.
Hereditary gingival fibromatosis is rare, and estimated to affect 1/750,000 people. Males and females are equally affected. It has not been reported in patients without teeth (edentulous).
Hereditary gingival fibromatosis is most commonly inherited in an autosomal dominant manner, meaning that each child of an affected parent has a 50% chance of developing the condition. However families with autosomal recessive inheritance and apparent maternal inheritance have also been reported.
There appears to be more than one gene mutation that can result in the same clinical appearance. In one large Brazilian family a mutation has been identified in the SOS(son-of-sevenless)1 gene on chromosome 2. SOS1 is an oncogene involved in cell growth and the Ras oncogene pathway. This mutation has been designated GINGF1 (Mendelian Inheritance in Man classification MIM135300). The mutation of a second form, GINGF2 (MIM605544) has been mapped to chromosome 5. And in GINGF3 (MIM 609955), the mutation in at least seven families has also mapped to chromosome 2, but not to the SOS1 gene. GINGF3 may therefore represent the most common form of the condition. The specific genes involved in GINGF2&3 have not yet been identified. Two unrelated Chinese families with a maternally-inherited form have been mapped to chromosome 11. However, as the clinical presentation is the same with these different mutations, it is likely they affect the same cellular pathway.
Overgrowth of the gums can also occur as a component of inherited syndromes (syndromic gingival fibromatosis).
Hereditary gingival fibromatosis presents as a localised or generalised overgrowth of the attached keratinised gums of variable severity. If mild, it involves only the interdental papillae (gum between the teeth), but usually it affects the marginal gum (gum over the teeth) also. In the localised form, the overgrowth occurs mainly on the lip/cheek side of the gum of the lower molars and the maxillary tuberosity. The generalised form affects all 4 quadrants of the mouth and may extend onto the palate.
Gum enlargement usually begins after the second permament incisor teeth erupt, usually by the age of 10 years. Rarely it starts with the first primary deciduous milk teeth or very rarely earlier. At least two of the GINGF3 famlies have characteristically developed the changes with the first teeth and this may prove to be characteristic of this form of the condition.
In one family it was observed that gum growth occured most rapidly during loss of the milk teeth and eruption of the permanent teeth.
The gum swelling is of normal pink colour, but is firm to the touch with little tendency to bleed. It affects both the upper and lower jaw and both the inner (lingual-palatal) and outer (labial-buccal) aspects of the gums.
The gum overgrowth progresses slowly to cover the teeth either partially or completely. If severe it may extend also over the palate.
Two patterns have been identified:
The degree of gum overgrowth varies considerably, even among members of an affected family. There is variability in the number of teeth involved (extent) and the volume of excess gum (severity).
The gum overgrowth can cause:
Hereditary gingival fibromatosis is a clinical diagnosis based on the following criteria:
The pathology of the excessive gum tissue shows dense fibrous connective tissue (collagen, elastin and oxytalan fibres) with reduced numbers of blood vessels. GINGF3 shows relatively few cells in the connective tissue whereas GINGF1 has increased cell numbers. The overlying epithelium is often thickened with characteristic elongated rete reaching deep into the connective tissue.
Good oral hygiene is important, and may be the only treatment required when gum enlargement is minimal.
The excessive gum tissue can be removed by:
Recurrrence is usual, although the rate at which this occurs is variable.
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