Prednisolone-Induced Black Hairy Tongue

Dear Editor,

Black hairy tongue (BHT) is a benign mucosal condition characterized by the presence of elongated filiform papillae on the dorsum of the tongue. It is also known as hyperkeratosis of the tongue, lingua villosa nigra, nigrites linguae, keratomycosis linguae, or melanotrihia lingua. Here, we report a case of prednisolone-induced black hairy tongue with dermoscopic findings.

A 53-year-old man presented with blackish discoloration of the dorsum of the tongue and a burning sensation on having meals for the last 15 days [Figure 1]. He had been taking low dose prednisolone (10 mg) on and off by himself for air-borne contact dermatitis since last six months. There was no history of chronic smoking, any addiction, or excessive black tea or coffee intake. He maintained good oral hygiene with daily cleansing. On close examination, elongated black filiform papillae were seen on the dorsum of tongue, sparing the lateral border. Buccal mucosa and palate appeared normal. We were not able to scrape off the discoloration. Bacterial and fungal culture revealed no growth. On dermoscopy, uniformly black filiform papillae giving “hair-like” appearance on a pink background were seen [Figure 2]. Steroids were tapered and discontinued over the next seven days. The patient was followed up after 30 days. On clinical examination, his tongue appeared completely normal [Figure 3]. After complete assessment, the index case satisfied the criteria for “probable/likely” category according to the World Health Organisation (WHO) Uppsala Monitoring Center (UMC) scale.[1]

Figure 1.

Black hairy projections on dorsum of tongue

Figure 2.

Long thin uniformly jet black filliform papillae giving “hair-like” appearance on a pink background

Figure 3.

Complete resolution 1 month after discontinuing Prednisolone

BHT may also appear as brown, yellow, green, blue, or even unpigmented, and usually affects the filiform papillae. Normally less than 1 mm in length, the elongated papillae can reach a length of 12–18 mm, and a width of 2 mm in BHT.[2] The known predisposing factors include smoking, excessive coffee/black tea consumption, poor oral hygiene, trigeminal neuralgia, general debilitation, xerostomia, and medication use. The exact mechanism of BHT induced by prednisolone is not known, but we hypothesize that

• Prednisolone often causes dry mouth, decreasing saliva production. Saliva naturally cleanses the tongue and prevents bacterial and fungal buildup.

• Prednisolone causes immunosuppression, reducing the body’s ability to fight infections, including bacterial or fungal overgrowth in the mouth, which can lead to a black hairy tongue.

• Corticosteroids, like prednisolone, may disturb the balance of normal oral bacteria and increase the risk of fungal infections, contributing to the condition.

Since microbiological culture ruled out any secondary infection along with BHT, dry mouth may be the preceding cause in our case. Dermoscopy can help in differentiating BHT from pseudo-hairy tongue and oral acanthosis nigricans. “Pseudo-hairy tongue” is a darkly stained tongue without elongated filiform papillae. Foods, tobacco, drugs like antibiotics, antidepressants, and bismuth subsalicylate can cause this. Acanthosis nigricans can involve the dorsum and lateral side of the tongue.

Previously, a “sea-anemone” dermoscopic appearance of hairy tongue in a chronic smoker has been reported.[3] Individual papillae showed distinct color variation with the base being a lighter shade than the tip, unlike in our case. There are multiple antibiotics reported to cause black hairy tongue, but only a single case of prednisolone-induced BHT in a polymyalgia rheumatica patient has been reported.[4]

We conclude that accurately identifying this benign condition, and differentiating it from other mimickers is important to avoid unnecessary investigations and treatments. Recognizing oral steroids as a potential cause of black hairy tongue is crucial in dermatology, as steroids are commonly prescribed for chronic inflammatory skin disorders. Early identification allows for timely dose adjustments or discontinuation, ensuring better management of side effects while maintaining effective treatment. Dermoscopy has been proven to be a crucial tool in identifying the condition before labeling it as any pigmentary condition. As it is a benign condition, the patient should be counseled about maintaining oral hygiene, and resolution on drug withdrawal.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)

The preparation of this manuscript was carried out entirely by the author without the use of artificial intelligence technologies.

Funding Statement

Nil.