The enzymatic activity and level of mitochondrial and cytosolic FH in lymphoblastoid and fibroblast lines from individuals with HLRCC were reduced compared to controls [32] and no cytosolic form was detected in FH deficient fibroblast lines with different levels of remnant FH activity (<1% to about 20%) [33]. Here, FH is linked to hereditary leiomyomatosis and renal cell cancer.