Myotonic muscular dystrophy is inherited in which pattern?

Myotonic muscular dystrophy is inherited in an autosomal dominant pattern. This means that only one copy of the mutated gene is necessary for an individual to express the disease. In the case of myotonic muscular dystrophy, the condition is associated with abnormal expansion of trinucleotide repeats (CCTG or CTG) in the DMPK gene in myotonic dystrophy type 1, or in the CNBP gene in myotonic dystrophy type 2, leading to the characteristic symptoms such as muscle stiffness (myotonia), weakness, and various systemic manifestations.

Because it is an autosomal dominant condition, affected individuals have a 50% chance of passing the mutated gene to their offspring regardless of the sex of the child. This is in contrast to X-linked conditions, which predominantly affect males, or autosomal recessive disorders requiring two copies of the mutated gene for manifestation, which typically affect both sexes equally but require a specific inheritance pattern from carrier parents. The polygenic option implies a trait that is influenced by multiple genes, which is not the case for myotonic muscular dystrophy, as it is primarily determined by a single genetic defect.