In "medicalese"...the sentence is, "MG is said not to be genetic." So, they are saying they haven't solid proof, as yet, however, it can be familial; passed down through generations, as Mike and Mastas know. Kathie said, there are markers. So, you may have MG, and your sibling may have another autoimmune disease that share this particular marker. Or, you both have the marker for MG. I can't speak to the autosomol...ah, recessive...I can't speak to the genetics because it's been too long, and besides, I didn't care what colour the guinea pig was; I just thought they were cute!