Leiden Muscular Dystrophy pages

Duchenne / Becker Muscular Dystrophies  (DMD / BMD)

(last modified February 28, 2004)


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DMD


DMD in females

In rare instances, females have been found which have a DMD or BMD phenotype. Theoretically, at a molecular level, several potential causes can be envisaged including translocations disrupting the DMD-gene, non-random X-inactivation and disease-causing mutations present in both DMD genes (i.e. on both X-xhromosomes). For details see "DMD/BMD in females".


Mental retardation

Mental retardation affects about one-third of DMD/BMD-patients, involving verbal skills more than non-verbal skills. In large patient cohorts the mean IQ is about 1 SD below average (Worden & Vignos [1962]). No direct association has been found between the type or position of DNA changes, protein expression and mental retardation (IQ scores). Still, both deletions (Hodgson et al. [1992], Nicholson et al. [1993]) and point mutations (Lenk et al. [1993]) in the distal part of the DMD gene have been reported to be associated with intellectual impairment. Felisari et al. [2000] explored the association between cognitive impairment and DNA deletions in the distal part of the gene, in particular when involving the distal brain dystrophin isoform Dp140. Comparison of neuropsychological and genetic data revealed an association between deletions in the distal part of the gene and cognitive impairment (p<0.001). Comparing deletions affecting Dp140 expression with those not altering Dp140 expression resulted in even greater significance.


X-linked dilated cardiomyopathy 

X-linked dilated cardiomyopathy (XLDC, sometimes abbreviated as XLDCM) is a clinical phenotype of dystrophinopathy which is characterized by preferential myocardial involvement without any overt signs of skeletal myopathy. It is a familial myocardial disease that presents with lethal congestive heart failure in young males in their teens or early twenties. A significant portion of XLDC-patients carry mutations in the dystrophin gene (Muntoni, Towbin). For details see "X-linked dilated cardiomyopathy and the DMD gene".


Age-related events

Van Essen et al. (PhD thesis) collected data on 473 Dutch DMD patients born and diagnosed during 1961-1982. Life-time events were analysed for birth years 1961-1974 to avoid possible effects of downward bias of age at diagnosis resulting from inclusion of birth years 1975-1982. Mean and median were calculated for age at onset, age at first walking, age at diagnosis, diagnostic delay, wheelchair-bound age and age at death (details see "Age-related events in DMD").



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