Woman diagnosed with rare black hairy tongue condition: Here's what it is

In a rare case, a 60-year-old woman suffered a bizarre reaction to antibiotics. Doctors found that the woman, who was battling rectal cancer and had started her treatment 14 months ago in Japan, had been taking minocycline, a common antibiotic used to treat everything from acne to pneumonia.

According to British Medical Journal Case Reports, to lessen the adverse effects of her chemotherapy, the woman had been taking about 100mg of minocycline per day to prevent panitumumab-induced skin lesions. The doctors, in the report, said that, as a result of the antibiotic, the patient was diagnosed with drug-induced hyperpigmentation and a black hairy tongue (BHT).

What is BHT?

As per the doctors, a black hairy tongue is a benign reversible condition that gives a dark and furry appearance. It results from a buildup of dead skin cells on the many tiny projections of papillae on the surface of the tongue that contains taste buds. Bacteria, yeast, tobacco, food and other substances can stain it.

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Besides discolouration of the tongue, a person might have altered taste or metallic taste in the mouth, bad breath and have gagging or tickling sensation.

BHT can occur as a side effect of various drugs as well. Since the patient was given both panitumumab and minocycline, it seemed unclear which drug caused the side effect. However, after examination, it was concluded that minocycline caused BHT since the patient's face also appeared to have grey hyperpigmentation. Minocycline turns black when oxidised and can lead to skin discolouration.

Upon concluding that minocycline caused BHT, the doctors discontinued the medication and the patient was switched to trifluridine and tipiracil hydrochloride plus bevacizumab combination therapy.

"Six weeks later, her facial pigmentation and BHT markedly improved. In this case, the disease course suggested that it was an adverse reaction to minocycline, with a causality rating of 'probable' according to the WHO-Uppsala Monitoring Centre Scale," the doctors wrote.

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The experts shared three important learning points from the case.

• If the patient develops skin hyperpigmentation, check the medications taken.
• Minocycline can cause skin hyperpigmentation as well as black hairy tongue.
• Discontinuation of the causative agent may improve skin hyperpigmentation and black hairy tongue.