If you close your eyes and picture a person with Duchenne muscular dystrophy (DMD), a boy or young man probably came to mind. Though boys account for the vast majority of patients with DMD, girls can also be affected.
DMD is often diagnosed later in girls due to its rare occurrence and generally milder symptoms compared to DMD in boys — but awareness and early management are still important.
Why does DMD occur in girls?
DMD is caused by a genetic mutation in one of the mother’s X chromosomes. It affects the production of the protein dystrophin, which protects muscles and helps in maintaining the membranes of muscle cells.
Learn more about DMD causes and risk factors
Males inherit one X chromosome from their mother and one Y chromosome from their father, whereas females inherit one X chromosome from their mother and one X chromosome from their father. A mother with a dystrophin mutation on one of her X chromosomes has a 50% chance of passing the mutation on to her son. Her daughter will have a 50% chance of inheriting it and being a carrier.
A man with DMD cannot pass the mutation on to his son, because the son will inherit his Y chromosome. His daughter, however, will receive the genetic mutation of his X chromosome and be a carrier.
In women and girls, inheriting a mutated X chromosome doesn’t automatically mean symptoms will develop. A female carrier of DMD has a second healthy X chromosome that works to balance out the faulty gene; her healthy X chromosome usually protects her from DMD.
In some cases, however, the healthy X chromosome can be inactivated, meaning the mutated X chromosome will be expressed. In other cases, symptomatic DMD occurs in girls if they have Turner syndrome, where one of their two X chromosomes is missing or damaged.
Around 2.5% to 20% of female carriers of DMD may be symptomatic, with varying severity of symptoms.
Symptoms of Duchenne in girls
In girls, DMD symptoms are usually less severe and appear later than in boys, which typically leads to a delay in diagnosis. Initial symptoms may include muscle weakness, frequent falls, difficulty climbing stairs, fatigue and elevated creatine kinase levels in blood tests, as well as symptoms of heart failure such as shortness of breath, dizziness, wheezing and coughing.
Girls affected by DMD may also experience a progressive weakening of their muscles and physical strength. However, it primarily impacts the muscles of the upper body, making them weaker than the lower limbs.
A greater risk of developing cardiomyopathy or heart failure has been reported in girls with DMD.
Managing DMD in girls
As with boys and young men, a multidisciplinary healthcare approach is required in managing DMD in girls and women. This may include medication (such as corticosteroids), physical therapy and orthotics (such as wrist splints) as well as close monitoring of cardiac and respiratory function.
If a member of your family has been diagnosed with DMD, speak to a genetic counselor to better understand the inheritance pattern of DMD. In female carriers, regular monitoring can mean early detection and treatment of symptoms.
Sign up here to get the latest news, perspectives, and information about DMD sent directly to your inbox. Registration is free and only takes a minute.
