GSTM1 and acute chest syndrome: Comparing our results with that of the Jamaican study with regards to commonest indications showed anemic crises represented 41.1% vs. 41.7% (aplastic + sequestration + hypoplasia), ACS (11.3% vs. 17.3%), stroke (7.3% vs. 11.9%); whereas the average Hb levels were in anemic crises (4.2 vs. 4.0 g/dL), ACS (6.2 vs. 5.0 g/dL), and in stroke (6.5 vs. 6.3 g/dL), respectively.