Ectodermal dysplasia is a rare group of inherited disorders. It was first
described by Charles Darwin in 1875. The disorders arise from disturbances
in one or more ectodermal structures and their accessory appendages. The
absence, or deficient function, of at least two derivatives of the ectoderm
constitutes a form of ectodermal dysplasia. Each combination of defects
represents another type of ectodermal dysplasia and has a specific name. At
least 150 different forms of ectodermal dysplasia have been identified; some
of the most common are presented here.
Individuals affected with ectodermal dysplasia have at least two of the
Absent or malfunctioning sweat glands. Temperature regulation can be
dysfunctional and lead to hyperthermia.
Dental anomalies, including missing or underdeveloped teeth.
Varying degrees of alopecia resulting from defective hair follicles.
Malformed or missing fingers or toes.
Malformed fingernails and toenails.
Cleft lip/palate, deficient saliva, hearing and visual defects, and
inadequate eye fluids and tears.
Neurologic and respiratory abnormalities may be present.
Autosomal dominant ectodermal dysplasia characterized
by the triad of palmoplantar hyperkeratosis, nail dystrophy, and alopecia.
Facial appearance, teeth, and sweating are normal.
Nail dystrophy and hyperkeratotic skin changes in a patient with
Fischer-Jacobsen-Clouston Syndrome; Hidrotic Ectodermal
Unknown. A higher incidence has been reported in the
French Canadian population, but it occurs in all ethnicities.
Autosomal dominant. The defect has been linked
Abnormality in the molecular structure of keratin
seems to be responsible for the disease.
Based on the typical clinical features and family
In contrast to the X-linked form of ectodermal
dysplasia (anhidrotic ectodermal dysplasia), most of the affected patients
have normal sweat and sebaceous glands, and the teeth are usually only mildly
affected (in contrast to the first description by Clouston). However, as in
other forms of ectodermal dysplasia, the patients suffer from severe
dystrophy of nails (thickened, striated, very slow growing, often
discolored) and hair (resulting in total alopecia, sometimes in infancy but
usually after puberty). Ultrastructural analysis of the hair shows an
altered organization of hair fibrils with loss of the cuticular cortex
suggesting a biochemical defect in the keratin of the integumentary system.
Skin changes include palmoplantar hyperkeratosis, which can involve the
periungual area and result in thickening of the fingertips with the aspect
of clubbing. Skin hyperpigmentation is common over the joints.