Repeat expansion disorders such as fragile X syndrome (FXS) and repeat contraction disorders such as facioscapulohumeral muscular dystrophy (FSHD) are typically caused by expansions or contractions in DNA repeats. Accurate measurement of the repeat region is essential but can be challenging and often requires PCR and Southern blot for accurate detection. PCR is accurate and fast but cannot size longer repeats. Southern blots use radioactive labeling, are labor intensive, and are inaccurate for repeat counts. Bionano EnFocus analysis can overcome these limitations by providing a single analysis and simple workflow using optical genome mapping (OGM) data that automates and enables accurate measurement of the repeat array size in as few as 3 days.