Newly married couple comes to OPD for preconception counselling . Both husband and wife are achondroplastic dwarfs. Which of the following should NOT be counselled to the couple?
Correct Answer: There is a 50 % chance of baby having normal stature
Description: Achondroplasia: Autosomal dominant inheritance, intelligence is typically normal. Most common non lethal skeletal dysplasia. 98 percent of cases are due to a specific point mutation in the FGFR3 gene 80 percent of cases result from a new mutation Characterized by long bone shoening that is predominantly rhizomelic, an enlarged head with frontal bossing, depressed nasal bridge, exaggerated lumbar lordosis, and a trident configuration of the hands. Condition is usually not diagnosed until late in pregnancy. When both parents have heterozygous achondroplasia (as in this case as homozygous achondroplasia is mostly lethal), there is a 75 % chance of the fetus being affected (25 % would be lethal homozygous and 50% would be affected heterozygous achondroplasia) and 25 % chance of fetus being normal. Father Aa x mother Aa A a A AA (lethal homozygous affected) Aa (non lethal heterozygous affected) a Aa ( non lethal heterozygous affected) aa (unaffected) The fetus can be homozygotes (which is 25 percent of the offsprings of heterozygous parents) the condition is characterized by greater long bone shoening and is lethal Affected women almost always require C- section because of the distoed shape of the pelvis
Category:
Gynaecology & Obstetrics
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