Dystrophic EB (DEB) may be inherited as a dominant (DDEB) or recessive (RDEB) trait. Major subtypes of DEB include:
Localized DDEB (previously encompassing nails only, pretibial, and acral DDEB)
Intermediate DDEB (previously known as generalized DDEB)
Intermediate RDEB (previously known as RDEB generalized intermediate, non-Hallopeau–Siemens RDEB)
Severe RDEB (previously RDEB generalized severe, Hallopeau–Siemens RDEB)
What are the common clinical symptoms of these DEB subtypes?
EB naevi (birthmarks or moles) may appear. The oral mucosa (the mucous membrane lining the inside of the mouth) may be affected with blistering, erosions, and scarring but changes are most extensive and marked in severe RDEB. Constipation and recurrent blistering and fissuring (cracking/splitting) around the anal margin (the area at the opening at the end of the bowel) are common in all forms of DEB, particularly the more severe types.
Which genes are affected?
All subtypes of DEB are caused by variants in the COL7A1 gene containing information needed to make collagen VII.
How is it inherited?
DDEB is inherited in an autosomal dominant manner (de novo inheritance is also possible).
RDEB is inherited in an autosomal recessive manner.
Rare subtypes of DEB
There are a number of rare subtypes of DEB. Click on the button below to find out more about the symptoms and affected genes of each.
Skin is usually fragile from birth or early childhood but limited to certain areas, mainly the fingers, toes, and nails. Sometimes only the nails are affected with progressive dystrophy (appearing thickened, damaged, misshapen, discoloured, and curvy) and loss, mainly of the toenails. Some people have blistering and scarring that mainly appears on skin covering the shinbone; these symptoms may not develop until later childhood or adulthood. The risk of developing squamous cell carcinoma (SCC) is also increased (albeit it to a lesser extent) and is less common than in severe RDEB and occurs later in adulthood.
INTERMEDIATE DDEB & RDEB
Although the recessive form tends to be more severe, it is usually not possible to tell the difference between these two types based on symptom appearance alone. Skin fragility, scarring, and milia (small, hard, pale nodules) are more generalized from birth or early childhood and tend to appear on bony areas like elbows, knees, ankles, and tops of the hands and feet. Mild flexion contractures (joints that cannot be straightened) or a striated-pattern of keratoderma (thickening of the skin) of the fingers, and limited fusion of the spacing between the fingers may occur, particularly in intermediate RDEB. The risk of developing squamous cell carcinoma (SCC) is also increased but less common than in severe RDEB and occurs later in adulthood. Oesophageal blistering and scarring are common. The eyes are usual affected leading to corneal erosions, pannus formation (growth of fine blood vessels onto the clear corneal surface), scarring, symblepharon (adhesion of the inner eyelid to the outer surface of the eyeball), and reduced clarity of vision. There may be a lack of sufficient nutrition owing to factors affecting eating, including oesophageal blistering, and increased metabolic demands due to chronic wounds, infection, and inflammation.
Skin blistering is widespread from birth with significant fragility from minor skin trauma. Chronic wounds are frequent in areas of repeated blistering. From infancy, blistering is more marked on bony areas causing extensive scarring that can lead to flexion contractures of the large joints (joints that cannot be straightened). Progressive pseudosyndactyly (fusion of the fingers and toes), flexion contractures, and resorption of the bone of the end of the fingers and toes lead to mitten deformities of the hands and feet. Areas of ulcerated skin is common and can appear on one or both sides of body, but in particular on the inner lower leg, and the tops of the feet and ankles. The development of aggressive squamous cell carcinoma (SCC) is very common and a frequent cause of death increasing in incidence from the teen years onwards, arising in areas of repeated trauma, wounds, and scarring. Progressive scarring leads to microstomia (contracture of the mouth) and ankyloglossia (reduced movement of the tongue), which can result in dental overcrowding and malalignment, and the development of secondary caries (cavities). Oesophageal blistering and scarring are common and urethral strictures may occur. Scarring alopecia (hair loss) and crusting are common with increasing age. Nails are usually lost progressively during the first several years of life. Anaemia due to iron deficiency and inflammation is common as is osteopenia, osteoporosis, and vertebral fractures possibly due to reduced mobility, chronic inflammation, vitamin D and calcium deficiency, and pubertal delay. Cardiomyopathy may rarely arise. Renal impairment and failure may occur as a result of acute kidney injury, post-streptococcal glomerulonephritis), renal amyloid, or IgA nephropathy. Lack of sufficient nutrition is common owing to factors affecting eating, including oesophageal blistering, microstomia, and dental caries, in combination with increased metabolic demands due to chronic wounds, infection, and inflammation.
The information above has been sourced from the ‘Consensus reclassification of inherited epidermolysis bullosa and other disorders with skin fragility’ article published in the British Journal of Dermatology https://doi.org/10.1111/bjd.18921