GSTM1 and pulmonary hypertension: Abnormal lung function, particularly, restrictive defects in Hb-SS, has been shown to be more prevalent in those with a severe disease pattern evident by recurrent vasoocclusive crisis and ACS, lower haemoglobin, raised markers of haemolysis, chronic leg ulcers, renal dysfunction, and raised pulmonary arterial pressures/pulmonary hypertension [5, 6, 16, 32].