Teddy Mak's family noticed that he was behaving a little oddly. The 49-year-old did not appear to fully understand them when they spoke, and seemed a little confused. He was also increasingly unsteady when he walked and appeared to be losing his muscle strength.
Mak (whose name has been changed for patient confidentiality reasons) had two pre-existing conditions: cardiomyopathy, or disease of the heart muscle, for which he was regularly taking medication, and bipolar affective disorder, which causes extreme mood swings.
Mak had been taking lithium to control the mood swings, and had successfully managed the condition for more than a decade. There had been no recent adjustments to his dosage.
But the unusual symptoms he was displaying did not fit any of his known conditions. After a few months of deterioration, his family decided to take him to hospital.
At Queen Elizabeth Hospital, the doctors noted he had a mild fever and was slightly confused when speaking. His ability to follow simple instructions, like "open your mouth", was mildly impaired.
Given his long history of taking lithium, which can cause serious side effects, or even death in the case of overdose, his blood was tested for lithium levels. They found 3.2 millimoles per litre. This was well above normal levels of between 0.5mmol/L and one mmol/L.