Muscular dystrophy affects people of all ages, races, and backgrounds, but the specific type determines who is most likely to develop it. Some forms almost exclusively affect boys, while others strike men and women equally, often not appearing until adulthood. Globally, the estimated prevalence across all forms is about 3.6 per 100,000 people, making muscular dystrophy rare but far from uncommon in absolute numbers.
Boys and Young Men: Duchenne and Becker MD
Duchenne muscular dystrophy (DMD) is the most common and most severe childhood form. It affects roughly 1 in 3,500 male births. Because the genetic mutation sits on the X chromosome, boys are overwhelmingly affected. Girls who carry the faulty gene sometimes experience mild muscle weakness or heart involvement, but full-blown Duchenne in girls is extremely rare.
Parents typically notice the first signs around age 2 or 3, often as difficulty running, climbing stairs, or getting up from the floor. Despite this, the average age at diagnosis has remained stubbornly around 5 years for the past three decades, meaning there is still a gap of roughly two years between when caregivers first notice something and when a confirmed diagnosis arrives. That delay has not improved over time, even with advances in genetic testing.
Becker muscular dystrophy is caused by mutations in the same gene but follows a milder course. It affects about 1 in 18,500 male births. Symptoms usually appear later in childhood or adolescence, and many people with Becker MD continue walking into their twenties or beyond. Like Duchenne, it is X-linked and primarily affects males.
Both Duchenne and Becker can arise from brand-new genetic mutations, not just inherited ones. Any newborn male can be affected regardless of family history.
Adults of Both Sexes: Myotonic Dystrophy
Myotonic dystrophy is the most common form of muscular dystrophy in adults, affecting at least 1 in 8,000 people worldwide. Unlike Duchenne and Becker, it follows an autosomal dominant inheritance pattern, meaning only one copy of the mutated gene is needed and it affects men and women equally.
Symptoms most often appear in a person’s twenties or thirties, though milder cases may not become obvious until mid to late adulthood. The hallmark is prolonged muscle stiffness after contraction (difficulty releasing a grip, for example), along with progressive weakness. It can also affect the heart, eyes, and hormonal systems, which is why it is sometimes called a multisystem disease. A severe congenital form can appear at birth, most often inherited from the mother.
Teens and Young Adults: Facioscapulohumeral MD
Facioscapulohumeral muscular dystrophy (FSHD) is one of the more common forms overall, with a prevalence estimated at about 12 per 100,000 in population-based studies. It is autosomal dominant, so it affects both sexes, though men tend to develop more severe symptoms.
FSHD typically begins in the teenage years or early twenties, starting with weakness in the face, shoulder blades, and upper arms. Progression is highly variable. Some people experience only mild limitations, while others eventually need a wheelchair. Because early symptoms can be subtle (trouble whistling, difficulty raising the arms overhead), diagnosis is sometimes delayed.
Childhood Through Adulthood: Limb-Girdle MD
Limb-girdle muscular dystrophy (LGMD) is not one disease but a collection of more than 30 genetic subtypes, all causing weakness concentrated in the hips and shoulders. It affects both men and women. Age of onset ranges widely, from early childhood to late adulthood, depending on the specific subtype.
The dominant forms (called Type 1) tend to appear later and progress more slowly. The recessive forms (Type 2) are more common overall and often begin in childhood or adolescence with a faster rate of decline. Because so many subtypes exist, LGMD can look quite different from one person to the next, which sometimes makes it one of the harder muscular dystrophies to diagnose.
Infants: Congenital Muscular Dystrophy
Congenital muscular dystrophy (CMD) is a group of inherited forms present at birth or within the first year of life. Affected babies show low muscle tone, weakness, and sometimes joint stiffness. The estimated prevalence is about 1 in 100,000, though experts believe the true number is higher now that genetic testing has improved.
CMD follows autosomal recessive inheritance in most cases, meaning both parents carry a copy of the faulty gene without being affected themselves. Some forms involve the brain and eyes as well as muscles, leading to intellectual disability or seizures, while others primarily affect skeletal muscle.
Racial and Ethnic Patterns
Muscular dystrophy occurs in every racial and ethnic group, but prevalence does vary. In the United States, surveillance data on Duchenne shows that about 62% of identified cases are non-Hispanic white, 20% Hispanic, 7% non-Hispanic Black, and roughly 11% other backgrounds. These numbers partly reflect population proportions, but research has found that the timing of diagnosis and access to specialist care differ across groups. Hispanic and Black children with Duchenne, on average, face longer delays before receiving a confirmed diagnosis and specialized services.
How Muscular Dystrophy Is Inherited
The inheritance pattern is the single biggest factor determining who is at risk for each type. There are three main pathways:
- X-linked recessive: The mutation is on the X chromosome. Mothers carry the gene and pass it to sons, who develop the disease. This is the pattern for Duchenne, Becker, and one form of Emery-Dreifuss MD.
- Autosomal dominant: One copy of the mutated gene from either parent is enough to cause disease. Men and women are equally affected. Myotonic dystrophy, FSHD, and some limb-girdle subtypes follow this pattern.
- Autosomal recessive: Both parents must carry the faulty gene. Each pregnancy carries a 25% chance of an affected child. Most congenital forms and many limb-girdle subtypes are inherited this way.
Some forms, like distal muscular dystrophy and Emery-Dreifuss, can follow more than one inheritance pattern depending on the specific mutation involved. And because new mutations can arise spontaneously, a family history of muscular dystrophy is not required for a child to be affected.