A man lost his sense of taste and had smelly breath when plaque built up on his tongue due to a rare kidney condition.
The 37-year-old plumber, who has not been named, had been eating a critically low amount of food for two months because his tongue was sore.
Doctors in Japan ran tests and found high levels of urea nitrate in his body, a sign of untreated kidney failure.
Because waste was not being filtered by the kidneys, the chemicals reacted with natural bacteria in his mouth. It triggered a build-up of plaque around the rim of his tongue.
The unusual oral symptom is called uraemic stomatitis, and has barely been reported in scientific literature before.
An unnamed man lost his sense of taste and had smelly breath when plaque (pictured) built up on his tongue due to a rare kidney condition
Because waste was not being filtered by the kidneys, a 'chemical irritant' was formed in the mouth, which caused the membranes of the tongue to go white
Dr Hiroyuki Yano and Dr Mitsuyo Kinjo Medicine, of Okinawa Chubu Hospital, Uruma, detailed the story in BMJ Case Reports.
On arrival, the man was alert, but said he had been suffering with fatigue, a lack of taste and no appetite for a while. Doctors said: 'White plaque on the rim of tongue was notable.'
They swiftly conducted laboratory tests which looked at levels of sodium, potassium, chloride, calcium, phosphate, nitrogen and various other chemicals in the body.
He had abnormally high levels of urea nitrogen in the blood, a condition called uraemia.
The body forms urea nitrogen, a chemical waste product, in the liver, which travels to the kidneys through the bloodstream.
Healthy kidneys filter urea and remove other waste products from the blood, which leave the body through urine.
If urea nitrogen levels are high, it signals that the kidneys, or liver, are failing to function.
The saliva is unable to break down the excess urea nitrogen, creating ammonia, which is a 'chemical irritant' in the mouth, the doctors explained.
This forms oral lesions or 'plaques' which are painful and white in colour, and a bad breath -