Manifesting Carriers of DMD or BMD
What is a Manifesting Carrier?
A manifesting carrier is a female who displays symptoms of
a condition that usually only affects males such as Becker and
Duchenne Muscular Dystrophy. Although it is a commonly held belief
that carriers merely pass on the disease and are unaffected, female
carriers can have similar muscular weakness as affected males and
for this reason are termed Manifesting Carriers. This condition can
occur with no known family history of BMD or DMD so all females who
are suspected of having any form of muscular dystrophy should be
tested to determine if they could be Manifesting Carriers because
of the genetic implications
All females inherit two copies of the X chromosome - one from
each parent. Each body cell needs only one functional X chromosome.
This is randomly determined, so that all females have a mixture of
cells in which the active X is either the maternal or the
All carriers of DMD have some cells in which the active X
carries the defect and problems arising from them will obviously
depend on the proportion of such cells and their distribution.
There is a theory that a compensatory mechanism could cause the
'normal' cells to produce enough dystrophin to make up the
deficiency - this has yet to be demonstrated. In very rare cases,
when the active X carrying the DMD gene is in the cast majority of
muscles cells the female carrier will have DMD as severely as
affected males. At the other end of the scale the carrier can be
unaffected. It is estimated that at least 10% of carriers may have
problems, which can vary from a mild generalized weakness to an
inability to walk, depending on how many muscles are affected. The
weakness can be asymmetric. There is also growing evidence that the
heart muscle can be affected in isolation which may not become
apparent until later in life. (sourced
For more information on Manifesting Carriers click
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THIS PAGE WAS REVIEWED 19 FEB 2016