Introduction
Rare heterogeneous group of inherited disorders characterized by dysplasia of tissues of ectodermal origin including skin, teeth, hair, nails, and eccrine glands.
History (HED)
According to Perabo et al ectodermal dysplasia may have been recorded as early as 1792 by Danz. In 1838, Wedderburn documented ectodermal dysplasia in a letter to Charles Darwin, describing a case of 10 Hindu male family members. Thurnham in 1848 reported 2 cases of hypohidrotic form. Similar cases were reported by Guilford and Hutchinson in 1883 and 1886 respectively. Weech, in 1929 introduced the term hereditary ectodermal dysplasia and suggested the term anhidrotic for those with inability to perspire. Felsher, in 1944, changed the adjective anhidrotic to hypohidrotic because the author agreed that person with hypohidrotic form are not truly devoid of sweat glands.
Classification
To date, more than 192 distinctive syndromes have been described with all possible modes of inheritance. The 2 major types are classified depending on sweat gland function:
Hypohidrotic (anhidrotic) ED:
Characterized by a clinical triad of hypodontia, hypohidrosis and hypotrichosis
- X-linked hypohidrotic ectodermal dysplasia (XLHED) “Christ–Siemens–Touraine syndrome” (75–95% cases, M/C form)
- Mutations in the inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase gamma (IKBKG), also called nuclear factor-kappaB (NF-kB) essential modulator (NEMO), gene are the most common single cause of incontinentia pigmenti (IP) in females and anhydrotic ectodermal dysplasia with immunodeficiency (EDA-ID) in males.
- Autosomal dominant & recessive HED (ADHED & ARHED) (5-25% cases)
- Ectodysplasin A receptor (EDAR) & ectodysplasin A receptor-associated death domain protein (EDARADD)
Hydrotic ED “Clouston’s syndrome” (rare)
Does not involve the sweat glands and is inherited as autosomal trait.
- Autosomal dominant inheritance: GJB6 gene (chromosome 13)
Clinical features
Hypohidrotic (anhidrotic) ED:
Clinical triad
- Hypotrichosis (partial/total alopecia)
- Scalp hair, eyebrows, and eyelashes are sparse, fine, and oftentimes lightly pigmented
- Hypo/adontia
- Hypohidrosis (reduced ability to sweat)→ Heat intolerance
- Eccrine sweat glands may be absent/sparse and rudimentary, particularly in those with hypohidrotic ED (HED)
Hidrotic ED:
Clinical triad
- Onychodysplasia (malformed, thickened, small nails)
- Hypotrichosis
- Palmoplantar hyperkeratosis (hyperkeratosis of the palms and soles)
Diagnosis
Diagnosis is based on the episodes of hyperpyrexia, lack or type of the hair, absence of teeth and tooth buds and tooth morphology. Peeling of the skin at birth, eczema, asthma, and frequent respiratory infections may be additional clues. However, during early infancy diagnosis is difficult because manifestations involving teeth, hair and inability to sweat are hard to detect.
Management
Optimal treatment requires a multidisciplinary collaborative efforts pediatric professionals, psychologist, ENT specialist and speech therapist.
Dental rehabilitation:
