<unk>  may refer to cardiac<unk> , metabolic<unk> nd single X syndrome, where an individual has a single X chromosome, typically described as Turner syndrome. The otherwise unidentifiable rare disease afflicting Brooke Greenberg and only about half a dozen other people in the world.
Syndrome X
Foster Kennedy syndrome
Loken Senior syndrome
Fragile X syndrome
Cardiac syndrome X
Triple X syndrome
Rajab-Spranger syndrome
Axenfeld syndrome