I have had a few "hereditary" diseases/syndromes/congenital abnormalities that nobody in my family has any knowledge of anyone else in my family having.

The first one discovered was the congenital abnormality pyloric stenosis which I had surgery to cure when I was 9 months old. The second one was a congenital abnormality of my having an extra bone in my feet's arch tendons, I still have the one in my right foot and the one in my left foot (which was golf ball sized at the time of removal) was removed when I was 4 days shy of 30 years old. I started developing asthma and allergies when I was about 22 years old - these are the only two disorders/diseases I have that have ANY traceability in my family and they have a STRONG traceability on both sides of my family. I also have TemperoMandibular Joint Disorder (TMJ or TMJD), osteoarthritis, lupus (possibly SLE), fibromyalgia, migraines, and had uterine fibroids with a cyst in one of my Fallopian tubes until I had my uterus and the affected Fallopian tube removed at the age of 34 and hypermobile thumb/wrist joints. Like I mentioned, the majority of these can be hereditary from what I have read but they cannot be found anywhere in my family going back to my grandparents' generation or down to my granddaughter's generation (but, then again, my granddaughter is only 1 year old and had her own set of lifethreatening congenital problems - 2 chambers in her heart, blood vessels to heart misplaced, all organs on wrong side of body and no or non-functioning spleen).