Recessive incisor hypodontia (RIH)
A specific form of hypodontia with an autosomal recessive mode of inheritance characterized by missing primary and permanent incisors and an increased inclination to eczema and asthma has been found in Finland (Pirinen et al, 2001) and apparently also in other countries (Fried, 1977; Akyuz et al, 1993; Lyngstadaas et al, 1996). RIH patients lack several lower incisors and upper permanent lateral incisors. In addition, some other permanent teeth can be missing. Half the patients have a corresponding primary tooth either missing or peg-shaped. Taurodontism of the molars is noted in more than half the patients. A large proportion of the patients (62%) report allergies manifesting as atopic skin (52%), and asthma (43%). Minor dental anomalies are seen in their parents and siblings in the form of missing and/or peg-shaped upper lateral incisors and missing third molar(s). The proportion of atopic diseases, both in the patients and their family members exceeds reported population prevalences. In a Finnish study, pedigrees of 31 families have been traced back at least five generations, and in two families, the parents of the proband had a common ancestor six and seven generations back, which supports the hypothesis of autosomal recessive inheritance (Pirinen et al, 2001).
Text adapted from Sirpa Arte: Phenotypic and genotypic features of familial hypodontia. Dissertation, Institute of Dentistry, University of Helsinki, Finland, 2001.
Text last edited 09.10.2003 by P.N. , page last created 10.12.2004 by P.N.