The transcription factor DUX4 is normally expressed during the 4-cell stage, activating various pathways leading to cleavage. This pathway shows how the abberrant expression of DUX4 in post-embryonic stages leads to several disturbations in skeletal muscle fibers, leading to adverse outcomes such as inflammation, apoptosis, and other processes contributing to facioscapulohumeral muscular dystrophy (FSHD). Low D4Z4 subunit methylation, which is caused either by low amount of D4Z4 subunits combined with a permissive 4q haplotype, or a mutation in genes involved with D4Z4 methylation, results in the expression of DUX4.