What causes blisters on the tongue and spots on the back of the throat?

Differential Diagnosis of Tongue Blisters and Throat Spots

The most common causes of blisters on the tongue and spots on the back of the throat are viral infections (particularly Coxsackievirus, herpes simplex virus, and Epstein-Barr virus), followed by bacterial pharyngitis (Group A Streptococcus), and less commonly, serious conditions like Stevens-Johnson syndrome or oral candidiasis. 1, 2

Primary Viral Etiologies (Most Common)

Viral infections account for the vast majority of cases presenting with these symptoms:

• Coxsackievirus and other enteroviruses cause characteristic vesicular lesions and ulcerations on the tongue and posterior pharynx, often presenting as herpangina or hand-foot-mouth disease 1, 2
• Herpes simplex virus produces painful vesicles that rupture into ulcers, typically affecting the anterior oral cavity and tongue 1
• Epstein-Barr virus (infectious mononucleosis) presents with severe pharyngitis, tonsillar exudates, and diffuse injection of oral and pharyngeal mucosae, often with petechiae on the palate 1, 3
• Adenovirus frequently causes exudative pharyngitis with prominent tonsillopharyngeal erythema that can mimic bacterial infection 1, 2

Key distinguishing viral features include:

• Presence of conjunctivitis, coryza, cough, or diarrhea strongly suggests viral etiology 2
• Discrete ulcerative lesions favor viral over bacterial causes 1
• Generalized lymphadenopathy (beyond anterior cervical nodes) and significant fatigue suggest mononucleosis 3

Bacterial Pharyngitis

Group A Streptococcus (GAS) is the most important bacterial cause requiring treatment:

• Presents with tonsillopharyngeal erythema with or without exudates, tender anterior cervical lymphadenopathy, and absence of viral features (no cough, coryza, or conjunctivitis) 1
• Petechiae on the palate may be present but are not specific 1
• Clinical diagnosis alone is insufficient—bacteriologic confirmation via rapid antigen test or throat culture is required 1
• The Centor criteria (fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough) help stratify probability, but even with 3-4 criteria, only 35-50% are confirmed streptococcal 1

Fungal Infections

Oropharyngeal candidiasis should be considered, particularly in immunocompromised patients:

• Presents as painless, creamy white, plaque-like lesions on buccal mucosa, tongue, or oropharynx that can be scraped off 1
• Less commonly appears as erythematous patches without white plaques on the palate or tongue 1
• Most common in patients with CD4+ counts <200 cells/µL or those on prolonged antibiotics/corticosteroids 1
• Diagnosis confirmed by KOH preparation showing yeast forms 1

Serious Conditions Requiring Urgent Recognition

Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN):

• Oral involvement characterized by painful mucosal erythema with subsequent blistering and ulceration, hemorrhagic sloughing of lips with dark adherent crusts 1
• Tongue and palate frequently affected; may extend to oropharynx, larynx, and esophagus 1
• Requires immediate recognition and transfer to specialized care—this is a medical emergency with significant mortality risk 1
• Associated with recent medication exposure (particularly sulfonamides, anticonvulsants, allopurinol) 1

Other serious considerations:

• Retropharyngeal or peritonsillar abscess presents with severe unilateral throat pain, drooling, trismus, and potential airway compromise 1, 4
• Epiglottitis is rare but life-threatening; avoid disturbing the airway if suspected 1, 4

Benign Self-Limited Conditions

Angina bullosa haemorrhagica:

• Sudden appearance of blood blisters on oral mucosa without identifiable systemic cause 5
• Affects mainly middle-aged and elderly patients, often related to minor trauma 5
• Benign and requires no treatment 5

Diagnostic Approach Algorithm

Step 1: Assess for emergency conditions

• Airway compromise, drooling, inability to swallow, severe toxicity → immediate ENT/emergency evaluation 4
• Recent medication exposure with mucocutaneous blistering → consider SJS/TEN 1

Step 2: Identify obvious viral features

• Conjunctivitis, coryza, cough, diarrhea → viral pharyngitis, supportive care only 1, 2
• Discrete vesicular/ulcerative lesions → likely viral (Coxsackievirus, HSV) 1
• Generalized lymphadenopathy + severe fatigue → consider mononucleosis testing 3

Step 3: Evaluate for bacterial pharyngitis

• Apply Centor criteria; if 3-4 criteria present, perform rapid antigen test 1
• If 0-2 criteria, testing generally not indicated 1

Step 4: Consider immunocompromised state

• White plaques that scrape off → KOH prep and treat for candidiasis 1
• Persistent or atypical lesions → biopsy may be required 6

Common Pitfalls to Avoid

• Do not diagnose streptococcal pharyngitis on clinical grounds alone—overlapping symptoms with viral causes make bacteriologic confirmation essential 1
• Do not miss SJS/TEN—any patient with mucosal blistering and recent medication exposure requires urgent evaluation 1
• Do not assume all white lesions are streptococcal exudates—candidiasis, EBV, and other viral infections can produce similar appearances 1, 3
• Do not overlook airway compromise—tongue swelling, drooling, or respiratory distress requires immediate intervention 7, 4