Congenital Muscular Dystrophy (CMD)

Causes / Inheritance

What causes congenital muscular dystrophy (CMD)?

CMDs are caused by changes (mutations) in genes that are important for healthy muscle function. These genes provide instructions for making proteins that help muscle cells stay strong, connected, and able to repair themselves.

Muscle fibers rely on a surrounding support system called the extracellular matrix (ECM). This network helps anchor muscle cells in place, allows them to transmit force, and supports communication and repair.

Many forms of CMD happen when these connections are weakened or disrupted. This can occur due to problems in:

• Extracellular matrix proteins (such as laminin 211 or collagen VI), which help anchor muscle fibers
• Modification (glycosylation) of alpha-dystroglycan, a key protein that connects muscle cells to the ECM
• Proteins inside muscle cells that support structure and function
• Defects in proteins that help maintain the structure of the nuclear envelope, a protective membrane that surrounds the cell’s DNA
• Other cellular systems, that participate in the assembly of proteins, recycling or energy pathways in the cell

When these proteins do not work properly, muscle cells become more fragile. Over time, normal muscle use can lead to damage, and the body may have a reduced ability to repair that damage, resulting in muscle weakness.

CMD symptoms begin early in life because many of the affected proteins are essential during muscle development before and shortly after birth.

It is important to note that early onset does not always mean more severe disease. The severity and progression of CMD vary widely depending on the specific subtype.

What are the inheritance patterns in CMD?

CMDs are genetic conditions, meaning they are passed down through families.

Autosomal recessive inheritance

Most types of CMD follow this pattern. A child must inherit two copies of the altered gene (one from each parent) to be affected. Parents who each carry one copy typically do not have symptoms.

Autosomal dominant inheritance

Some types of CMD are caused by a single altered gene copy. In these cases, an affected person has a 50% chance of passing the condition to their child.

Spontaneous mutations

In some families, CMD may appear unexpectedly, even when there is no known history of the condition. This can happen if parents are unaware they are carriers or if a new genetic change occurs.

Families who have questions about inheritance or future risk may benefit from speaking with a genetic counselor or a neuromuscular specialist.

Additional reading

• Pasrija D, Tadi P. Congenital Muscular Dystrophy. [Updated 2023 Jul 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK558956/
• Bönnemann CG et al. Members of International Standard of Care Committee for Congenital Muscular Dystrophies. Diagnostic approach to the congenital muscular dystrophies. Neuromuscul Disord. 2014 Apr;24(4):289-311. doi: 10.1016/j.nmd.2013.12.011.
• Zambon AA, Muntoni F. Congenital muscular dystrophies: What is new? Neuromuscul Disord. 2021 Oct;31(10):931-942. doi: 10.1016/j.nmd.2021.07.009.

Last reviewed June 2026.