RAD21 and inborn mitochondrial metabolism disorder: Primary PIPO, including sporadic or familial myopathy, neuropathy, mesenchymopathy, mitochondrial diseases, or neuropathy, has been linked to mutations such as ACTG2, SOX10, POLGI, FLNA, L1CAM, MYH11, MYLK, LMOD1, MYL9, RET, TYMP, RAD21, and SGOL1 (20–22).