I work in neuroscience, mostly Alzheimer's disease (AD), with some work in autism spectrum disorder (ASD). The work is in gene regulation and epigenomics. I'm familiar with monozygotic twin (MZ) discordance for AD and ASD and the methylome studies done in discordant MZ for those disorders. I began to become curious.
What disorders have never had MZ discordance reported in the literature? Even sickle cell has MZ discordant progression (Amin et al. 1991. Hemoglobin. 15:247-56). Do any disorders lack MZ discordance?