Recessive disease occurs when two mutated copies of a gene are inherited, one from each parent.Ìý
In recessiveÌýbestrophinopathy,Ìýa patient inheritsÌýtwo mutated copies of theÌýBEST1Ìýgene, one from each parent.ÌýThe onlyÌýbestrophinopathyÌýknownÌýto follow a recessive mode of inheritance is autosomal recessiveÌýbestrophinopathyÌý(ARB). In ARB, the presence of two mutated/defective copies of theÌýBEST1ÌýÌýgeneÌýcan lead toÌýtheÌýproduction of proteins that no longer function correctlyÌýor are completely absent, leading to disease.Ìý
WeÌýinherit one copy ofÌýtheÌýBEST1Ìýgene from our mother and one from our father. InÌýrecessive disease,ÌýbothÌýinheritedÌýcopiesÌýofÌýBEST1Ìýcontain a disease-causing mutation. In order to inherit two faulty copies of the gene,Ìýeach parent must have a faulty copy of the gene. Parents who have a mutatedÌýBEST1Ìýgene, but do not show any symptoms of disease are known as carriers. Two carrierÌýparents, with no diagnosedÌýbestrophinopathy,Ìýcan have a child withÌýARBÌýif the child inherits both mutated copies.ÌýÌý
If both parents have a singleÌýdefectiveÌýcopy of theÌýBEST1Ìýgene theÌýchances of having a child with recessive disease is 25%Ìýin each pregnancy, and there is a 50% chance of having a child who is a carrier.ÌýÌýThe image below shows this schematically:Ìý