D

Deletion mutation

The loss of genetic material from a chromosome or gene.

Desmin

A protein which forms the medium sized filaments of muscle cells. Individuals with Desmin Myopathy have an abnormal assembly of these filaments.

Diplopia

Double vision caused by weakness of the eye muscles. When the muscles on each side are not affected equally it causes the eyes to point in slightly different directions.

Distal

Away from the centre of the body.

Distal myopathies

A group of conditions predominantly affecting the distal muscles.

DNA

Deoxyribonucleic acid, the chemical basis of genes, in which information is encoded for synthesising proteins Each cell’s chromosomes contain about two metres of DNA, although it is so thin that it is barely visible even with the most powerful microscope. If the entire DNA in a human body were stretched end to end it would be long enough to reach the moon and back about 10,000 times.

Dominant inheritance

In a dominant inheritance pattern, an individual will show signs of the disorder if he or she possesses one of a pair of altered genes. He or she has a 50% chance of passing on the altered gene to his or her children, producing an affected child.

Duchenne muscular dystrophy

A genetic disorder in which muscle cells break down, and are eventually lost, causing progressive muscle weakness. The condition usually affects only boys and is caused by a lack of dystrophin protein.

Duplication mutation

The repetition of part of a chromosome or gene.

Dysferlin

A protein absent in individuals with limb girdle muscular dystrophy type 2B and Miyoshi myopathy.

Dysphagia

Difficulty in swallowing.

Dystrophin

The protein missing in individuals with Duchenne muscular dystrophy and reduced in those with Becker muscular dystrophy.

Dystrophin-glycoprotein complex

The binding of dystrophin to other proteins forming a critical link between the inside and outside of muscle cells.

Dystrophy

The word originates from two Greek words, ‘dys’ (‘faulty’) and ‘trophe’ (‘nourishment’). Muscular dystrophy refers to a group of disorders characterised by progressive muscle weakness and loss of muscle tissue.