Hypohydrosis in Hypodontia

Hypodontia is a feature of many ectodermal dysplasia (ED) syndromes. As sweat glands are structures of ectodermal origin, reduction of the sweat pore count is a feature of some EDs, notably the hypohydrotic or anhydrotic types. An association between a reduced sweat pore count and non-syndromic hypodontia has previously been reported in a study of unrelated individuals. Objective: To investigate the hypothesis that apparently non-syndromic hypodontia is actually a microform ED, this study sought to establish whether sweat pore counts are reduced in familial non-syndromic hypodontia. Methods: 36 families with familial hypodontia were examined for disturbances of structures of ectodermal origin other than the dentition. 25 families were excluded because gross features suggestive of an ED were detected in one or more individuals. From the remaining 11 families, finger pad impressions were taken of 77 subjects, including 45 with hypodontia. Also included was a family with the clinical features of Witkop tooth-nail syndrome (TNS). Sweat pores were counted along a 5mm section of dermal ridge on the pad impressions. Two counts were carried out on middle and ring fingers, and an average count calculated for each individual. Results: A linear relationship was confirmed between pore count and log₁₀age. Most data points for both hypodonts and normals lay within the 95% CI previously described for normals. However two families, including the supposed TNS family, demonstrated a significantly reduced pore count in hypodonts, microdonts and even apparently clinically normal individuals. One TNS individual had no detectable pores. Conclusion: The hypothesis that all hypodonts are likely to have a reduced sweat pore count is incorrect. Most do not, and are truly non-syndromic, but a minority of hypodonts do, and may be affected by a microform hypohydrotic-type ED.

Financial support for this project was given by Guy’s and St Thomas’ Charitable Trust.