July 1985, Volume 35, Issue 7

Case Reports

Congenital Ectodermal Dysplasia

Arif-un-Nisa Naqvi  ( Department of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan Agricultural Research Council, Islamabad. )

Abstract

Two cases of phenotypically similar ectodermal dysplasia characterised by reduction of hair, diminished sweat pores, missing teeth and somewhat cracked and abnormal skin were studied to understand the genetic basis of this disorder with the help of pedigrees. The mode of inheritance in one case was suggested to be x-linked where as in the other case it was autosomal recessive. (JPMA 35 225, 1985).

Introduction

Congenital ectodermal dysplasias (EDs) are a group of familial disorders that affect tissues and organs of ectodermal origin.1 Ectodermal dysplasia in humans is a complex and heterogeneous group which has been classified into thirty two conditions2.
An autosomal recessive inheritance was suggested for a form of hypohydrotic ectodennal dysplasia in which sweat pores were reduced in number but were not completely absent3
The, mode of inheritance in two siblings affected with ectodermal dysplasia with sensorineural hearing loss was suggested to be autosomal recessive.1
Bixler et al.4 have reported two cases of ectrodactyly-ectodermal dysplasia clefting (EEC) syndrome and suggested an autosomal dominant inheritance with incomplete penetrance for the syndrome.
An association between ectodermal dysplasia, cleft lip, cleft palate and scrubbing brush hair was seen and this disorder was determined by an autosomal gene5.
The present study includes two cases of phenotypically similar ectodermal dysplasia characterised by reduction of hair, diminished sweat pores, missing teeth and somewhat cracked and abnormal skin. An attempt has been made to understand the genetics of this disorder with the help of pedigrees.
Pedigrees.
Figure 2 contains a pedigree of ectodermal dysplasia in which 1-4 and 1-5 are first cousins whereas all other couples of the pedigree are unrelated. The propositus is the resident of Islamabad and is forty years old.
Figure 3 shows the pedigree of a family of Rawalpindi district. A brother and sister are affected with ectodermal dysplasia and most of the marriages in this family are consaguineous.

Discussion

Symbols generally used in a pedigree are shown in figure 1.

The pedigree shown in

figure 2 can be best explained by postulating an x-linked recessive inheritance for the trait. According to this hypothesis 11-10 is a carrier and the trait is expected to affect her male offspring only. The female offspring 111-2 can be normal as well as a carrier. For the following reasons it is less likely that the trait is determined by an autosomal recessive gene.
(a) As the couple 11-9 and 11-10 are not blood relatives the probability that both of the are heterozygous carriers is relatively low considering the low incidence of ectodermmal dysplasia in the general population.
(b) On the basis of this hypothesis, irrespective of sex, a quarter of the offspring are expected to beaffected. While the pedigree shows two out of the three offspring affected and both the affected persons happen to be males, though the possibility that it is merely a coincidence cannot be ruledout.


The pedigree shown in Figure 3 can be explained by postulating an autosomal recessive nature of the trait.

The cases reported by Crump3 and Mikaelian1 also have similar genetic basis. The couple 11-6 and 11-7 are first cousins and probably both are heterozygous carriers because Iwo out of seven of theft offspring, which is roughly a quarter are affected. Some of the early deaths referred to in the pedigree might have been caused by ectodermal dysplasia.

Reference

1. Mikaelian, D.O., Der Kaloustian, V.M., Shahin, NA. and Barsoumian, V.M. Congenital ectodermal dysplasia with hearing loss. Arch. OtolaryngoL, 1970;92:85.
2. Freire-Maia, N. Ectodermal Dysplasias. Hum. Hared., 1971;21 : 309.
3. Crump, 1. Hypohidrotic ectodermal dysplasia; a study of sweat pores in the x-linked form and in a family with probable autosomal recessive inheritance. 3. Pediat., 1971; 78 : 466.
4. Bixler, D., Spivack, 3., Bennett, J. and Christian, J.C. The ectrodactyly-ectodermal dysplasiaclefting (EEC) syndrome; report of 2 cases and review of the literature. Clin. Genet., 1972; 3: 43.
5. Sonafe, J.\\L, Larregue, M., Nougue, 3. and Lamon, P.

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