ectodermal dysplasia

Christ
Siemens Touraine syndrome: a case report. Pigmented nevus at the arms and forearms.
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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.

Epidemiology

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

Pathology

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) ; position of the gene at Xq12-q13.1 (XLHED-gene) 
  • the remaining 20% have no sexual predilection
Associations

Associations often occur with mutations in theTP63 gene.

  • midfacial defects, mainly cleft lip and palate
  • EEC syndrome (ectodermal dysplasia, ectrodactyly, and clefting) 
  • AEC syndrome (ankyloblepharon, ectodermal dysplasia, and cleft lip/palate)
  • Rapp-Hodgkin syndrome
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 categorized into a number of subgroups.

Clinical presentation

  • sparse hair (atrichosis or hypotrichosis) that is light in color, 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

Prognosis

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

Differential diagnosis

Clinical differential considerations include:

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