At initial presentation in ED, patients in the severe LGIB cohort were more likely to have active per-rectal bleeding (43.8% vs. 30.3%, P = 0.001, Table 2), tachycardia (HR ≥ 100, 22.6% vs. 9.5%, P < 0.001), hypotension (SBP < 90 mmHg, 6.2% vs. 0.5%, P < 0.001) and anaemia (Hb < 9 g/dL, 46.9% vs. 5.0%, P < 0.001). The gene discussed is GSTM1; the disease is anemia (phenotype).