Whilst homozygous FH mutations cause fumaric aciduria, a condition associated with infantile encephalopathy and brain malformations [39], heterozygous FH mutations followed by the loss of heterozygosity of the second allele cause Hereditary Leiomyomatosis and Renal Cell Cancer (HLRCC) [13], [40]. The gene discussed is FH; the disease is fumaric aciduria.