Dominant dystrophic epidermolysis bullosa
Information for patients and carers
Autumn 2003
EB is a group of rare
inherited conditions in which the skin blisters extremely easily. There are three main
types of EB. Each is a distinct disorder – as different from the other forms of EB as
chicken pox is from measles. If you have dominant dystrophic epidermolysis bullosa, (DDEB)
often known as dystrophic EB, you cannot later develop one of the other forms of EB
(simplex or junctional). Dominant dystrophic EB is not the same as recessive dystrophic
EB, which is a much more serious condition.
Fortunately, dominant dystrophic EB is one of the milder forms of EB. Blisters appear
during early childhood, usually by six months of age, but occasionally they do not develop
until later in life. Sometimes a blister is present at birth. Blisters often become more
numerous as a result of the normal rough and tumble of childhood. They tend to occur over
vulnerable sites such as knees, ankles, elbows and knuckles. As blisters heal, they leave
small scars, which in children and adolescents may be conspicuous because of their
pinkish- purple colour. During adult life, blisters usually become less frequent and scars
fade to match the colour of the surrounding skin. Dominant dystrophic EB may sometimes be
so mild that an affected adult regards the skin as normal. The severity of DDEB does vary
enormously and not all patients are so fortunate. Each DDEB sufferer needs individual
assessment, advice and treatments specific for his or her needs.
Blisters are unfortunately often painful. To prevent them from enlarging, and thus to keep
pain and subsequent scarring to a minimum, blisters need to be burst using either a
sterile needle or sterile scissors. This should be done as soon as possible after a new
blister has formed; sometimes, if blisters are numerous, it may be necessary to burst
blisters several times a day. Supplies of suitable needles can be obtained from your
general practitioner. After bursting, a suitable dressing should be applied to the site,
both to relieve pain and to prevent infection. Up-to-date advice regarding suitable
dressings can be obtained from the DebRA nurse specialists, but as a general principle, it
is essential to avoid the use of adhesive dressings, as these will tear the skin when they
are removed. Suitable non-adhesive products include Melolin, which is available over the
counter or on prescription. A layer of Vaseline applied to the shiny skin-contact surface
will prevent Melolin sticking. Mepitel, which is only available on prescription, is an
excellent non-adherent dressing. A lightweight tubular bandage such as Tubifast will be
necessary to hold dressings in place.
Antiseptic lotions or creams may sometimes be needed. Protection of vulnerable areas of
skin will help keep the number of blisters to a minimum. Careful selection of footwear is
also important. The DebRA team will give individual advice.
Although dominant dystrophic EB affects predominantly the skin, it can sometimes cause
other problems as well. Constipation is quite common, but prevention and treatment are
usually straightforward with a combination of a high fibre diet and if necessary, gentle
laxatives. If constipation is ignored, it can cause painful splitting of the skin at the
anus.
Dental caries can be a problem for those who develop blisters within the mouth, as
brushing teeth can be painful. The teeth are completely normal in DDEB, but just as in
everyone else, they do need to be cared for! The DebRA team can give some practical tips.
Regular visits to the dentist are essential.
The scarring process often causes thickening of the big toe nails and occasionally of
other nails as well. A very small proportion of people develop slight swallowing problems
and a few adults have difficulty in straightening their fingers fully.
The blistering tendency in DDEB is caused by a very minor abnormality of the DNA in one
gene, rather like a spelling mistake. The gene controls production of a protein (collagen
VII) in the skin. In DDEB this protein is not formed correctly and is weaker than normal.
The result is that minor knocks cause separation of the layers of skin which would
normally be held firmly together by collagen VII. The gap between these layers fills with
fluid forming a blister.
Everyone has two genes controlling the production of collagen VII, one gene inherited from
each parent. In DDEB, only one of the two genes is faulty. When a person with DDEB has a
child, there is a 1 in 2 chance each time a pregnancy occurs, that the faulty gene will be
passed on to the child, equivalent to the chances of a tossed coin landing
“heads” side up. Both males and females can be affected and can pass on the
condition. Sometimes a person with DDEB has normal parents. In this situation there are
several possibilities. The spelling mistake on the DNA can occur for the first time at
conception even though both parents have normal genes. Other more unusual patterns of
inheritance are known to occur occasionally, but these are very rare. It is often possible
to look at inheritance patterns by taking simple blood samples.
If you have any form of surgery, it is important to tell the surgical team that you have
DDEB and to warn them that their usual dressings will not be suitable for you. Special
precautions might be appropriate during anaesthesia and surgery. The surgical team should
be made aware of your skin problems well before the date of your planned operation so that
they can discuss your needs with your dermatologist or with the DebRA nurses.
At present there is no cure for any of the various forms of EB, but research projects,
many funded by DebRA, are underway in several centres around the world. The results are
exciting and encouraging, but many unanswered questions remain.
H. M. Horn, Department of Dermatology, Royal Infirmary of Edinburgh.
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