Isodisomy is a form of uniparental disomy in which both copies of a chromosome, or parts of it, are inherited from the same parent. It differs from heterodisomy in that instead of a complete pair of homologous chromosomes, the fertilized ovum contains two identical copies of a single parental chromosome.^[1][2] This may result in the expression of recessive traits in the offspring.^[3] Some authors use the term uniparental disomy and isodisomy interchangeably.^[4]

This genetic abnormality can result in the birth of a normal child who has no obvious disability.^[1] It is associated with abnormalities in the growth of the offspring and in the placenta.^[2] Isodisomy may be a common phenomenon in human cells, and "might play a role in the pathogenesis of various nonmalignant disorders and might explain local impaired function and/or clinical variability."^[5]