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 – sometimes which smells similar to urine.
A CT scan showed both kidneys were smaller than usual indicating long-lasting kidney failure. At this stage, it was unclear why or when the man had got kidney failure.

The man’s tongue returned to normal after treatment. He needs to continue haemodialysis three times a week, however
Exposure to environmental pollutants, toxins or certain medications, severe dehydration or chronic disease can lead to kidney failure.
The doctors noted the man had smoked five cigarettes per day for 17 years. Smoking lowers blood flow to important organs like the kidneys and can make kidney disease worse.
Around one in 50 people will progress from chronic kidney disease to kidney failure, according to the NHS.
Despite symptoms of kidney failure including irregular heartbeat and swelling of the legs, ankles and feet, the man had none of these.
Treatment was started straight away, including haemodialysis, which removes excess waste from the body, effectively replacing the job of failed kidneys.
Within a week, the patient’s appetite and taste returned to normal, and the white patches on his tongue disappeared, the doctors said,
He needs to continue haemodialysis three times a week, however.
The doctors wrote: ‘Uraemic stomatitis is a rare complication of advanced renal failure.’
The number of people who are affected by uremia stomatitis or uraemia is unclear.