What is the inheritance pattern of myotonic muscular dystrophy?

Myotonic muscular dystrophy (MMD) follows an autosomal dominant inheritance pattern. This means that only one copy of the mutated gene, inherited from an affected parent, is sufficient to cause the disorder. Individuals with the condition typically have a 50% chance of passing the affected gene to each of their offspring.

This condition is characterized by muscle wasting and weakness, as well as myotonia, which is the inability to relax muscles after contraction. MMD is caused by mutations in genes responsible for the production of proteins that are crucial for muscle health. In particular, the most common form (MMD1) results from a CTG trinucleotide repeat expansion in the DMPK gene.

Understanding the inheritance pattern is important for genetic counseling and risk assessment in families affected by the disorder. In contrast, the incorrect options range from X-linked recessive, which involves disorders primarily affecting males and carried by females, to autosomal recessive, where two copies of the mutated gene are necessary for the manifestation of the disease, and X-linked dominant, which often leads to more severe manifestations in females. None of these accurately describes the inheritance of myotonic muscular dystrophy, reinforcing that it is classified as autosomal dominant.