Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys because the disorder is X-linked recessive. Muscle weakness usually begins around the age of four and worsens quickly. A classic sign of DMD is trouble getting up from lying or sitting position, as manifested by a positive Gowers’s sign. When a child tries to arise from lying on his stomach, he compensates for pelvic muscle weakness through use of the upper extremities: first by rising to stand on his arms and knees, and then “walking” his hands up his legs to stand upright. Another characteristic sign of DMD is pseudohypertrophy (enlarging) of the muscles of the tongue, calves, buttocks, and shoulders (around age 4 or 5). The muscle tissue is eventually replaced by fat and connective tissue, hence the term pseudohypertrophy. Most are unable to walk by the age of 12.

Creatine kinase (CPK-MM) levels in the bloodstream are extremely high. Scoliosis is also common. Some may have intellectual disability. Females with a single copy of the defective gene may show mild symptoms.

About two thirds of cases are inherited from a person’s mother, while one third of cases are due to a new mutation. It is caused by a mutation in the gene for the protein dystrophin. Dystrophin is important to maintain the muscle fiber’s cell membrane. Genetic testing can often make the diagnosis at birth.


The muscle-specific isoform of the dystrophin gene is composed of 79 exons, and DNA testing (blood test) and analysis can usually identify the specific type of mutation of the exon or exons that are affected.

DNA testing confirms by MLPA the diagnosis in most cases.