Macrosatellite

In genetics, macrosatellites are the largest of the tandem repeats within DNA. Each macrosatellite repeat typically is several thousand base pairs in length, and the entire repeat array often spans hundreds of kilobases. Reduced number of repeats on chromosome 4 (D4Z4 repeats) causes euchromatization of local DNA and is the predominant cause of facioscapulohumeral muscular dystrophy (FSHD). Other macrosatellites are RS447, NBL2 and DXZ4,  although RS447 is also commonly referred to as a "megasatellite."