A young man who followed a strict vegetarian diet developed hypotension due to vitamin B12 deficiency in a landmark case that has prompted calls for screening of other at-risk patients.

The 27-year-old man is believed to be the first reported case of hypotension associated with vitamin B12 deficiency in a young person, write doctors from Qatar and the US in BMJ Case Reports.

The previously fit and well Nepalese man, who had been a strict vegetarian throughout his life, presented to the Hamad Medical Corporation in Qatar with a four-week history of intermittent low-grade fever and vomiting.

This was accompanied by gradual worsening of a yellow discolouration of the skin, eyes and urine, and pale stools.