Ectodermal dysplasia

Ectodermal dysplasia (ED) refers to a heterogeneous group of genetic disorders that cause abnormal ectoderm development. The effect is a non-progressive defect in the development of two or more tissues derived from embryonic ectoderm. 

ED is rare with an estimated prevalence of 1:17,000. It can occur in any race but is most commonly seen in Caucasians.

Genetics

More than 192 distinct disorders have been described:

  • the most common form, which occurs in 80% of ectodermal dysplasias is X-linked recessive hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome), where incidence in male is estimated at 1:100,000 births and is inherited through female carriers (carriers-incidence is 17.3:100,000 women) 1; position of the gene at Xq12-q13.1 (XLHED-gene) 2
  • the remaining 20% have no sexual predilection
Associations

Associations often occur with mutations in theTP63 gene.

Classification

There are four primary ectodermal dysplasia (ED) defects:

  • ED1: trichodysplasia (hair dysplasia)
  • ED2: dental dysplasia
  • ED3: onychodysplasia (nail dysplasia)
  • ED4: dyshidrosis (sweat gland dysplasia)

These are further categorised into a number of subgroups.

  • sparse hair (atrichosis or hypotrichosis) that is light in colour, coarse and excessively brittle
  • abnormal peg-shaped or pointed teeth, particularly the upper incisors and cuspids which are typically conical
  • missing teeth (anodontia or hypodontia) and taurodontism of deciduous molars
  • inability to sweat due to lack of sweat glands (anhidrosis or hypohidrosis) this causes intolerance to heat and over heating can rarely be a cause of death
  • fingernails and toenails may be absent, thick, abnormally shaped, discoloured, ridged, slow growing, or brittle 
  • lack of breast development
  • absent fingers or toes 
  • recurrent infections
  • missing ears and hearing difficulties

People with ectodermal dysplasia have normal intelligence, life expectancy and can lead a full and productive lives. 

Clinical differential considerations include:

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Article information

rID: 16833
Section: Pathology
Tags: cases, dental
Synonyms or Alternate Spellings:
  • Christ-Siemens-Touraine syndrome
  • Ectodermal dysplasia (ED)
  • Ectodermal dysplasias

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