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Diseases

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Opitz G/BBB syndrome


Other Names for this Disease
  • BBB syndrome
  • G syndrome
  • GBBB syndrome
  • Hypertelorism hypospadias syndrome
  • Hypertelorism with esophageal abnormality and hypospadias
More Names
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Inheritance


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How is Opitz G/BBB syndrome inherited?

Opitz G/BBB syndrome often has an X-linked pattern of inheritance. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes (the other sex chromosome is the Y chromosome). In most cases, males experience more severe symptoms of the disorder than females. This is because females have two different X chromosomes in each cell, and males have one X chromosome and one Y chromosome. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons, because fathers only pass a Y chromosome on to their sons (which is what makes them male). In some cases, an affected person inherits a MID1 mutation from an affected parent, while in other cases, it may result from a new mutation in the affected individual. These cases occur in people with no history of the disorder in their family.[1]

A female who has the X-linked form of Opitz G/BBB syndrome has a 25% (1 in 4) chance to have a daughter with the mutation, a 25% chance to have a son with the mutation, a 25% chance to have an unaffected daughter, and a 25% chance to have an unaffected son. This also means that there is a 50% chance, with each pregnancy, for the child to inherit the mutation. A male with the X-linked dominant form of Opitz G/BBB syndrome will pass the mutation on to all of his daughters and none of his sons.

Researchers have also described an autosomal dominant form of Opitz G/BBB syndrome caused by a deletion in one copy of chromosome 22 in each cell. In some cases, an affected person inherits the chromosome with a deleted segment from a parent, while in other cases, the condition results from a new deletion in the affected individual. These cases occur in people with no history of the disorder in their family. Males and females with the autosomal dominant form of Opitz G/BBB syndrome usually have the same degree of severity of symptoms.[1] A male or female who has the autosomal dominant form of Opitz G/BBB syndrome has a 50% (1 in 2) chance with each pregnancy for the child (male or female) to inherit the genetic abnormality.
Last updated: 6/17/2011

References
  1. Opitz G/BBB syndrome. Genetics Home Reference. November 2007; http://ghr.nlm.nih.gov/condition/opitz-g-bbb-syndrome. Accessed 6/17/2011.