NEW YORK, Feb 07 (Reuters) -- If you have acne, it may be making you blue -- literally. Long-term users of minocycline, an acne medication, may end up with a "blue smile" -- that is, a permanent discoloration of the facial bones visible through the gums, according to a letter in this week's issue of the medical journal The Lancet.
The drug, minocycline hydrochloride, is one of the most commonly prescribed antibiotics for fighting acne and is routinely taken for months or even years.
Minocycline has been known to discolor skin, nail beds, thyroid gland, cartilage, bones and teeth since it was introduced 30 years ago, but this was thought to occur only in rare cases. Now, a study of 331 patients taking minocycline for more than six months reveals that 1 out of 10 patients develop a blue or blue-black discoloration of their oral cavities. And 1 out of every 5 patients taking the drug for four years develop the bone pigmentation.
"I was very surprised by the high number considering the drug has been around that long and there have only been a handful of patients reported with (the side effect)" said author, Dr. Drore Eisen, a dentist and dermatologist at Dermatology Research Associates in Cincinnati, Ohio.
However, the discoloration isn't necessarily obvious, according to Eisen. Only 5 patients out of 33 were aware of their pigmentation, because it could only be seen when they smiled.
"As (minocycline) gets degraded, it gets deposited in the bones of the mouth, so it's actually not in gums, it's in the bone," he said. The blue color shows up in the mouth in areas where the gums are particularly thin.
"It's not the gums immediately around the teeth, because the gums there are pretty thick. But if you go up higher (or lower in the mouth) it becomes very transparent, so you can actually see the bone," he said. "In people who have a big smile, in which their lips rise up, you are going to see that pigmentation."
The blue color, which may be due to the deposition of insoluble salts in bone when minocycline is broken down, is probably permanent, according to the Ohio researcher. Of 16 patients who stopped taking the drug, 15 were still blue -- albeit, slightly faded -- a year later.
Patients treated with high-dose minocycline for long periods of time should be screened for the blue pigmentation and switched to another type of antibiotic, Eisen concluded.
"It's not dangerous, but it's important to recognize because if the medication is not altered, the pigmentation will become darker and can be confused with other disorders," he said. Such illnesses include Addison's disease, a life-threatening failure of the adrenal glands, which can give a brownish tint to the area around the mouth.
SOURCE: The Lancet (1997;349:400)
