Hypohidrotic ectodermal dysplasia.

X linked hypohidrotic ectodermal dysplasia was studied in the dentition of both affected males and carrier females. Hypodontia was more severe in males than females and there were differences in the pattern of tooth absence between the sexes. Abnormal crown form, with the maximum diameter of the teeth being apically displaced, was noted particulady in the anterior teeth. Taurodontism was commonly seen radiographicaily. X linked hypohidrotic ectodermal dysplasia (XHED) is expressed fully in males and partially in heterozygous female carriers. It is characterised by sparse hair, diminished sweating, and dental anomalies, particularly hypodontia (congenitally missing teeth). The prevalence in the population has been assessed as lying between 1:10 000 and 1:100 000 male live births.' There are a number of reports of the dental findings in individual cases and their families, together with four substantial investigations. Nakata et a12 determined tooth size in 49 subjects in 15 families with XHED. Affected males and carrier females both showed consistently smaller mesiodistal tooth crown diameters than did unaffected persons. Radiographs were taken but were not reported on separately. Airenne3 studied 11 males from nine families together with their relatives. He confirmed the reduction in mesiodistal diameter and showed that this was also true for the buccolingual dimension in both affected males and heterozygous females. Radiographs were usedonly to assess thedegreeofhypodontia. Soderholm and Kaitila4 investigated six patients and their five Department of Child Dental Health, University of Bristol Dental School, Lower Maudlin Street, Bristol BS1 2LY. P J M Crawford Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff CF4 4XN. M J Aldred, A Clarke Correspondence to Mr Crawford. mothers, the heterozygous mothers having hypodontia affecting four or more teeth. A detailed analysis of the dental anomalies does not seem to have been published. Radiographs were not reported to have been taken routinely. Clarke' examined 35 families with XHED. He found the mean number of deciduous teeth absent in affected males to be 16x4 (out of the normal 20) and the mean number of permanent teeth absent to be 23-7 (out of the normal 28, excluding third molars). Seventy-five percent of obligate carrier females had 'distinctly abnormal' permanent teeth. Radiographs were only occasionally available. It was the aim of this study to assess the dental findings in affected males and heterozygous female members of families with XHED using 'distant examination' techniques. Subjects, materials, and methods Thirty-four British families with XHED were identified as part of a clinical and genetic study of this disorder.' S Both males and females from these families had previously been examined by one of the present authors (AC). The District Dental Officer for each of these subjects was subsequently asked for cooperation in arranging a clinical and radiographic dental examination. Forty of the 42 approached kindly agreed. Patients were then contacted by letter explaining the nature and purpose of the investigation and enquiring of them their willingness to participate and the name of their present dental surgeon (if any). Letters were sent to 140 persons and 62 affirmative replies were received. Either the patient's own dental surgeon or the appropriate Community Dental Service was supplied with an explanatory letter, a copy of the patient's signed consent form, details of the ethical approval, and an examination form. It was intended that, wherever possible, the special examination would form part of the patient's routine recall and the radiographs would be available for return to the practitioner. Practitioners were asked to allocate teeth examined clinically to either 'normal', 'conical/peg', or 'reduced' categories on the basis ofcrown form and size. For convenience, the last two groupings were subsequentlycombined byus togiveasingle 'abnormal' code for data analysis. The completed examination Received for publication 27 March 1990. Revised version accepted for publication 31 July 1990. 181 group.bmj.com on October 28, 2017 Published by http://jmg.bmj.com/ Downloaded from