Last update: 12/12/2007

Background to disease

OMIM 310200 (gene OMIM 300377)

Duchenne and Becker muscular dystrophies are caused by mutations in the DMD gene, located at Xp21.1 – Xp21.3. DMD is a lethal X-linked recessive disease with onset in childhood, BMD results in a milder phenotype and is not lethal. Patients have developmental delay, progressive muscle wasting affecting skeletal and cardiac muscle. Muscle wasting is rapid, with most children being wheelchair-bound by age 13. Proximal muscle weakness causes a waddling gait and difficulty climbing. Patients have also difficulty in standing from sitting on the floor and use the Gower manoeuvre to rise.

Female carriers of DMD mutations can be affected due to skewed X-inactivation, Turner syndrome or recombination in the DMD gene.

There is a high rate of new mutations with approximately 1/3 of sporadic cases being due to new mutations. 65% of males with DMD have a deletion of one or more exons, 7% have a duplication of one or more exons, and 28% have truncating point mutations. Introns 7 and 44 of the DMD gene are mutation hotspots.

Laboratory Analysis

Analysis for this disease is now carried out by the Northern Genetics Laboratories under a reciprocal arrangement (GENLYNC). Please contact them directly regarding information regarding turnaround time and sensitivity. Local samples should still be sent via the Yorkshire Regional Genetic Laboratory where they will be forwarded as whole blood as appropriate. DNA from these samples can be stored in the Yorkshire Regional Genetic Laboratory if it is anticipated that future tests may be required (please indicate clearly on referral card if required).