I imagine the actual Medical Condition is rare, it is usually commonly called "Fish Odour Syndrome", and if you have this, caused by your Genes, there is no known cure, just things that can be done.
I think that most of the few smelly J.W's that we encountered suffered from a lack of personal cleanliness.
One Elder told me he was tasked with telling a "Sister" about her Pong, as he drove to her house he agonised about how to approach the matter in a kindly way, from an oblique angle at first, and then gently getting on to advice on how to be clean and not smell. He said that when he got in there, he just found himself saying :
"Frankly Sister, you Stink !" Ha Ha. It worked though ! but it took the help of some lovely young J.W "Sisters", to make sure it lasted and there was no relapse, they regularly visited her, and made sure she kept clean, and her smell was at least acceptable !