Novel haemoglobin mutation (α127Lys → Glu) increases oxygen affinity and has a minor effect on haptoglobin binding

► Novel Hb was fortuitously detected in carrier with erythrocytosis on A1c analysis. ► Molecular modelling showed critical functional location of mutation. ► Functional analysis showed increased O2 affinity and decreased haptoglobin binding. ► Family studies showed only a mild response to tissue anoxia. ► Substitution correlated with structure, function and phenotype changes.