Although few in number, examples of mutations in miRNA genes associated with human diseases, including monogenic Mendelian diseases, indicate that sequence variants can impact miRNA genes by disrupting various aspects of their function, including the efficiency of miRNA processing/miRNA level, the 5p/3p strand ratio, the shift in DROSHA/DICER1 cleavage sites generating alternative isomiRs, and the efficiency of the recognition and silencing of target genes (summarized and discussed [15]). Here, DICER1 is linked to glycogen storage disease VI.