Genetic heterogeneity of gingival fibromatosis on chromosome 2p

Gingival fibromatosis (GF) occurs in several genetic forms as a simple Mend elian trait, in malformation syndromes, and in some chromosomal disorders. Specific genes responsible for GF have not been identified. An autosomal do minant form of hereditary gingival fibromatosis (HGF, MIM 135300) was recen tly mapped to chromosome 2p21 in a large Brazilian family and there was an earlier report of GF in a boy with a cytogenetic duplication involving 2p13 -->p21. We thus hypothesised that a common gene locus may be responsible fo r GF in both the Brazilian family and the boy with the chromosome 2p duplic ation. We performed additional genetic linkage studies on the Brazilian fam ily and molecular cytogenetic studies on the patient with the cytogenetic d uplication to correlate more precisely the genetic interval of the HGF phen otype with the duplicated 2p interval. Additional linkage analysis of new f amily members resulted in refinement of the candidate region for HGF to an 8 Mb region. Molecular cytogenetic analysis of the 2p13-->p21 duplication a ssociated with GF showed that the duplicated region was proximal to the can didate interval for HGF. Thus, our results support the presence of two diff erent gene loci on chromosome 2p that are involved in GF.