General description
Dystrophic Epidermolysis Bullosa (DEB) is the second most common form of EB: it accounts for 25% of EB cases (less than 1 in 1,000,000 of newborns).
DEB is transmitted by the parents, either in recessive or dominant mode depending on the type of DEB.
This pathology manifests at birth or during early childhood.
The signs and symptoms of this illness vary according to the person affected. In benign cases, blisters form mainly on the hands, feet, knees and elbows. However, severe cases of this pathology can present with blisters all over the body, which may lead to blindness, disfigurement, erosion of the oesophagus and serious mutilation of the extremities of the limbs.
DEB variants are characterised by the separation of the skin beneath the lamina densa.
These types cause atrophic scarring with milia. They are divided into two groups dependent on whether they are transmitted via a dominant or recessive mode:
- DEB recessive type (RDEB)
- DEB dominant type (DDEB)
Although the types differ in severity, their symptoms overlap significantly and they are caused by mutation of the same gene.
Sub-types of DEB
Autosomal recessive type (RDEB)
This type is characterised by recessive autosomal transmission and is the most severe form of DEB, a little less common than the dominant form. It exists itself in two forms:
- Hallopeau-Siemens
- Non-Hallopeau-Siemens
The Hallopeau-Siemens (RDEB-HS) form of EB is the most severe, since it causes major disability. It manifests initially with a general eruption of blisters, however these are predominantly localised on the extremities of the limbs. It includes dental complications and mucous lesions including oral, anal and oesophageal stenosis which can cause malnutrition and retard growth. Scarring of the cutaneous lesions is slow and abnormal and is accompanied by milia, terminating in the characteristic atrophic lesions that cause disability (syndactylies, contraction when flexing the limbs). During childhood, repeated blistering and long periods of pathological scarring result in a significant handicap: it becomes more and more difficult to walk and perform everyday movements. Anal erosion makes defecation painful. Death often occurs during the first three decades of life as a result of infectious complications, malnutrition with anaemia, retarded growth and even secondary amyloidosis. Spinocellular carcinoma often appears on the most affected areas of skin and mucous membrane.
The Non-Hallopeau-Siemens form is distinguished from classic Hallopeau-Siemens by the absence of serious disfigurement and a particularly variable clinical appearance in relation to the severity and extent of the lesions. Repeated ulcerations on the limbs may be associated with the development of spinocellular carcinoma.
In RDEB, ultrastructural examination shows hypoplasia or a reduction in the number of collagen fibrils. Ultrastructural anomalies are much more severe in RDEB-HS.
Autosomal dominant type (DDEB)
The principal form, called Cockayne-Touraine (DDEB-CT), is characterised by a generalised eruption of blisters appearing at birth or in very early childhood. In the majority of cases, this does not affect the mucous membrane and predominantly affects trauma zones (hands, feet, elbows, knees). The scarring dystrophies are also limited to these areas and are not as serious as in RDEB. They cause atrophic skin which has the texture of a cigarette paper, more rarely presenting keratosis, milia and ungual anomalies, the most common of which are pachyonychia. The teeth are normal. The function of the hands and feet are not compromised and as the fragility of the skin becomes less severe with age, the overall prognosis is favourable. There are no extracutaneous visceral attacks.
Ultrastructural examination shows hypoplasia or a reduction in the number of collagen fibrils.
Transmission : How do people inherit Dystrophic Epidermolysis Bullosa