We present the case of a 76-year-old male with history of Type II diabetes presenting for routine HbA1c testing. The HbA1c profile via capillary electrophoresis (CE) revealed the presence of an unknown haemoglobin peak of 19.3% in Zone 1. Blood film showed microcytosis, hypochromia, poikilocytosis and red cell dimorphism. The unknown haemoglobin migrated in the HbH position on the Sebia Capillarys3 Hemoglobin(E) program and on High Pressure Liquid Chromatography (HPLC). Many HbH bodies were detected on Brilliant Creysl Blue (BCB) staining and biochemistry was consistent with haemolysis. A presumptive diagnosis of acquired HbH disease, or alpha thalassaemia-MDS (AT-MDS), was determined. The acquired nature was determined by previously normal red cell indices and HbA1c chromatogram. AT-MDS is an acquired disorder that most commonly occurs due to rare somatic mutations in the ATRX gene, or less commonly chromosome 16p. There is a male predominance (6:1) and the median diagnosis age is 68. These mutations occur in 0.2–‘.8% of MDS cases and produce a more severe alpha thalassaemia phenotype when compared to germ line mutations of ATRX. This case highlights a novel diagnostic pathway for a rare disease and emphasises the importance of investigating ‘incidental’ haemoglobin variants detected during HbA1c testing.