What are the differentials, diagnostics, and treatments for a white coating on the tongue?

White Coating on Tongue: Differential Diagnosis, Diagnostics, and Treatment

Most Common Diagnosis

Oral candidiasis (thrush) is the most likely cause of white coating on the tongue and should be diagnosed clinically with confirmation by scraping and KOH preparation microscopy. 1

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Differential Diagnosis

Primary Infectious Causes

• Oral candidiasis presents as creamy white, plaque-like lesions on the tongue and buccal mucosa that can be scraped off, revealing an erythematous base underneath 1
• Three clinical patterns exist: pseudomembranous (classic white plaques), erythematous (red patches after white coating removal), and angular cheilitis 1
• Risk factors include immunosuppression (HIV/AIDS, chemotherapy), diabetes, denture use, prolonged antibiotic or corticosteroid use, and xerostomia 1

Non-Infectious Causes

• Oral leukoplakia appears as white patches that cannot be scraped off and requires biopsy to exclude dysplasia or malignancy, particularly in patients over 40 with tobacco/alcohol use 2, 3
• Geographic tongue presents with irregular white borders surrounding red patches and requires no treatment 3
• Hairy tongue shows elongated filiform papillae with white, yellow, or brown discoloration and requires no specific treatment 3
• Oral hairy leukoplakia (Epstein-Barr virus-related) appears as vertical white corrugations on lateral tongue borders in immunocompromised patients 3

Physiologic Coating

• Bacterial tongue coating from poor oral hygiene presents as diffuse white coating associated with halitosis, most commonly caused by plaque accumulation 4, 5, 6

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Diagnostic Approach

Clinical Examination

• Attempt to scrape the white coating with a tongue depressor: if it removes easily revealing red mucosa underneath, this strongly suggests candidiasis 1
• Examine for distribution pattern: diffuse coating suggests physiologic accumulation or candidiasis; localized non-scrapable patches suggest leukoplakia 3
• Assess for associated findings: erythema, ulceration, induration, or asymmetry warrant biopsy 2, 3

Laboratory Confirmation

• For suspected candidiasis: obtain scrapings for KOH preparation showing budding yeast and pseudohyphae, or culture on fungal-selective media 1
• Direct microscopy with KOH is sufficient for diagnosis in most cases; culture is reserved for refractory cases to assess antifungal susceptibility 1

When to Biopsy

• Mandatory biopsy indications: unilateral lesions, non-scrapable white patches, induration, ulceration, patients over 40 with tobacco/alcohol use, or lesions persisting beyond 2 weeks of appropriate treatment 2, 3
• Biopsy differentiates benign lesions from premalignant leukoplakia or squamous cell carcinoma 3

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Treatment

For Confirmed Oral Candidiasis

First-Line Therapy

• Fluconazole 100 mg orally daily for 7-14 days is superior to topical therapy and should be first-line treatment 1
• Alternative: Clotrimazole troches 10 mg dissolved in mouth 5 times daily for 7-14 days for mild cases or when systemic therapy is contraindicated 1
• Alternative: Nystatin suspension 100,000 U/mL, 4-6 mL swish-and-swallow 4 times daily for 7-14 days 1

Refractory Cases

• Itraconazole solution 200 mg orally daily is effective in approximately two-thirds of fluconazole-refractory cases 1
• Amphotericin B oral suspension 100 mg/mL, 1 mL swish-and-swallow 4 times daily for itraconazole-refractory disease 1
• Intravenous amphotericin B 0.3 mg/kg/day as last resort for severe refractory disease 1

Adjunctive Measures

• Remove and disinfect dentures thoroughly if present 1
• Address underlying immunosuppression when possible (optimize HIV treatment with HAART) 1
• Avoid suppressive antifungal therapy unless recurrences are frequent or disabling, to reduce resistance development 1

For Physiologic Tongue Coating

• Mechanical tongue cleaning with tongue scraper or soft toothbrush daily is the most effective intervention for reducing bacterial coating and associated halitosis 4, 5, 6
• Chlorhexidine 0.2% mouthwash twice daily may provide additional benefit for reducing coating and malodor 2, 5
• Improve overall oral hygiene as this is the strongest determinant of tongue coating presence 6

For Other Causes

• Oral hairy leukoplakia: treat with oral antivirals (acyclovir or valacyclovir) 3
• Leukoplakia: requires biopsy and management based on dysplasia grade; may need surgical excision or close surveillance 3
• Geographic tongue and hairy tongue: reassurance only, no treatment needed 3

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Critical Pitfalls to Avoid

• Do not assume all white tongue coatings are benign: failure to biopsy persistent, non-scrapable, or unilateral lesions in high-risk patients (age >40, tobacco/alcohol use) can delay cancer diagnosis 2, 3
• Do not rely on fungal cultures for initial candidiasis diagnosis: clinical appearance and KOH preparation are sufficient; cultures are only needed for refractory cases to guide antifungal selection 1
• Do not prescribe chronic suppressive antifungal therapy routinely: this promotes resistance development; reserve for patients with frequent disabling recurrences 1
• Do not overlook denture hygiene: denture-related candidiasis requires thorough denture disinfection in addition to antifungal therapy for cure 1
• Do not ignore underlying systemic conditions: recurrent or refractory candidiasis warrants evaluation for immunodeficiency (HIV testing, diabetes screening) 1