How do YECs explain hereditary diseases?

(Note that this is the same Question as https://christianity.stackexchange.com/questions/104555 , but asking for a different group's views.) Hereditary diseases include color blindness, Down's syndrome, hemophilia, sickle cell disease, and albinism. Sexually transmitted diseases includes chlamydia, gonorrhea, herpes, HIV/AIDS, and syphilis, at least some of which can also be transmitted from parent to child. All of these diseases require that another person — either a parent or sexual partner — has previously had the condition. If all of humanity starts from Adam and Eve, this implies that Adam and Eve must have carried all of these diseases in order for them to be passed on to their offspring. Did God created Adam and Eve loaded with all those diseases? How do Christians which deny Common Descent and believe that all humans are descended from Adam and Eve some few thousand years ago explain this situation?