NM_000143.4:c.6C>T is a synonymous variant (p.Tyr2=) in exon 1 of FH, which encodes fumarate hydratase. This variant is present in gnomAD at low overall frequency: 0.025% in v2.1 (45/178,374 alleles) and 0.013% in v4.1 (199/1,544,456 alleles), with grpmax filtering allele fractions of 0.018% and 0.029% respectively, meeting PM2 at supporting strength.¹ The variant has been classified as Benign or Likely benign by multiple reputable clinical laboratories in ClinVar (Variation ID 184570): 4 laboratories classify as Benign and 6 as Likely benign, with criteria provided. The consensus among established clinical testing laboratories meets BP6 at supporting benign strength.² SpliceAI predicts no splicing impact (max delta score 0.00), and the variant does not lie within a known mutational hotspot or the fumarate lyase domain. No functional studies, cosegregation data, de novo reports, or case-control analyses are available for this variant.³ PVS1, PS1, PS5, PM5, PP2, BP1, BP3, PM3, and PM4 are not applicable to this synonymous variant. The remaining pathogenic criteria (PS2, PS3, PS4, PM1, PM6, PP1, PP3, PP4, PP5) are not met. All benign criteria except BP6 are not met or not assessed. BA1 and BS1 are not met as the overall allele frequency is below respective thresholds. The net evidence tally consists of one supporting pathogenic criterion (PM2_supporting) and one supporting benign criterion (BP6_supporting). Under ACMG/AMP 2015 combination rules (PMID:25741868), when benign and pathogenic criteria cancel at the supporting level, the variant defaults to Variant of Uncertain Significance (VUS).⁴