Is Lesch Nyhan syndrome inherited ?
How is Lesch Nyhan syndrome inherited? Lesch Nyhan syndrome is inherited in an X-linked recessive manner. A condition is X-linked if the changed (mutated) gene responsible for the condition is located on the X chromosome. The X chromosome is one of the two sex chromosomes; females have two X chromosomes, and males have one X and one Y chromosome. Females who have one mutated copy of the responsible gene (on one of their X chromosomes) usually do not have the condition and are referred to as carriers. This is because they still have a working copy of the responsible gene on their other X chromosome. Males with one mutated copy of the responsible gene have signs and symptoms of the condition (they are affected) because they do not have another X chromosome with a working copy of the gene. This is why X-linked recessive disorders, including Lesch Nyhan syndrome, occur much more frequently in males. Lesch Nyhan syndrome is caused by mutations in the HPRT1 gene. A female who is a carrier of Lesch Nyhan syndrome has a 50% chance of passing on the mutated HPRT1 gene in each pregnancy. This is because a carrier female will randomly pass on one of her X chromosome to each child. Sons who inherit the mutated gene will be affected, and daughters who inherit the mutated gene will be carriers. This means that with each pregnancy, a female who is a carrier has a: 50% (1 in 2) chance of having an unaffected son or daughter 25% (1 in 4) chance of having an affected son 25% chance of having a carrier daughter