Mabel Wong, 85, had been feeling tired. Her health had always been good, but her recent bouts of fatigue were growing worse. She also started to feel short of breath, and her family members noticed that she looked pale and wan.
Initially, Wong (whose real name has been withheld for reasons of patient confidentiality) tried to brush her symptoms off as a passing phase or a natural decline of energy that came with age. But the fatigue grew worse and lingered for two months.
When Wong felt so weak that she could no longer leave the house, she finally sought medical help.
Tests showed that Wong was anaemic, with a low red blood cell count and a haemoglobin count of six grams per decilitre of blood, which is about half the normal level.
A low count of haemoglobin - the protein molecule in red blood cells that carries oxygen - would have caused her breathlessness.
Wong's red blood cells were also abnormally large, and she had low levels of white blood cells and platelets. Her doctor suspected that something was wrong in her bone marrow, where red and white blood cells and platelets are made. He ordered a bone marrow biopsy, which showed the presence of a high percentage of very primitive blood cells called blasts.