autosomaldominant

Autosomal dominant refers to a pattern of inheritance in which a single copy of a mutant allele on an autosome is sufficient to produce a phenotype. Individuals with one affected allele typically show the trait or disorder, and affected persons often have an affected parent. The condition can affect both males and females with roughly equal frequency, and transmission can occur across generations, sometimes with a vertical pattern in family pedigrees.

The genetic basis of autosomal dominant conditions includes several mechanisms. Haploinsufficiency occurs when loss of one functional copy reduces gene product below a critical level. Dominant-negative mutations produce an abnormal protein that interferes with the normal one. Gain-of-function mutations create a new or enhanced activity. Penetrance can be complete or incomplete, and expressivity can be highly variable, leading to differences in severity among affected individuals. De novo mutations may arise in an affected child without a prior family history.

Counseling and testing considerations emphasize a 50% risk to offspring for each pregnancy, assuming one parent is affected and the other is unaffected. Recurrence risk remains the same in each pregnancy, though de novo cases occur. Genetic testing and cascade testing of relatives can clarify risk, while mosaicism can complicate predictions. Management is condition-specific and may involve surveillance for associated complications, lifestyle adjustments, and targeted therapies.

Common autosomal dominant disorders include Marfan syndrome, Huntington disease, familial hypercholesterolemia, neurofibromatosis type 1, and autosomal dominant polycystic kidney disease. Understanding the pattern aids diagnosis, risk assessment, and family planning.