Doctors were already concerned about this patient drinking herbal tea made from cannabis and antiretrovirals, even before realising it probably also contained arsenic.

The 37-year-old, who had HIV, presented to doctors in Bloemfontein, South Africa, complaining of three weeks of lower limb weakness and urinary and faecal incontinence.

The weakness generally worsened throughout each day, and by evening he could not stand

He also reported episodes of intense abdominal cramps over the past four months, each lasting about a week and resolving spontaneously, plus a history of untreated hypertension, smoking and use of illicit drugs, including cannabis.