However, this association reached genome-wide significance in the discovery cohort (P=5.4 × 10−14) and has clear biologic and clinical underpinnings: the variant encodes p.Thr67Ile in cystathionine gamma-lyase, a cytoplasmic enzyme that converts cystathionine into cysteine, and even more convincing, prior reports have identified homozygosity for this same missense mutation as a cause of cystathioninuria (MIM#219500)9, 10, a benign autosomal recessive disorder characterized by accumulation of plasma cystathionine and increased urinary cystathionine excretion. The gene discussed is CTH; the disease is cystathioninuria.