Step I down's syndrome

[ctizzle13498]

Uworld is confusing me. It says Fragile X syndrome is the #1 cause of mental ******ation by inheritance (which makes sense since it is X-linked, and Down Syndrome isn't passed down by inheritance)

However, another question dealing with Down Syndrome states that "Down Syndrome is the 2nd most common cause of mental ******ation." What would be the first?

 

[Ty Webb]

Uworld is confusing me. It says Fragile X syndrome is the #1 cause of mental ******ation by inheritance (which makes sense since it is X-linked, and Down Syndrome isn't passed down by inheritance)

However, another question dealing with Down Syndrome states that "Down Syndrome is the 2nd most common cause of mental ******ation." What would be the first?

Fetal alcohol syndrome is MCC overall. And downs usually isn't "inherited", in the strictest sense, as it's usually from a novel nondisjunction event in maternal meiosis I (ie the parents don't have the disease, nor is it expressed in any of the previous generations, so doesn't usually show "inheritance")