A patient presents with fissuring, erythema and crusting at both angles of the mouth. Which organism is most commonly implicated?

Correct answer: A. Candida albicans

• A. CORRECT. Angular cheilitis is most commonly a candidal infection, frequently in a mixed infection with Staphylococcus aureus. Saliva pooling in the commissural folds creates a warm, moist, macerated environment that Candida colonizes readily.
• B. Treponema pallidum can produce oral lesions in secondary syphilis, but split papules at the commissures are far less common than candidal angular cheilitis.
• C. Herpes simplex causes recurrent vesicular lesions on the vermilion border and perioral skin, unilateral and preceded by prodromal tingling — a different pattern entirely.
• D. Streptococcus pyogenes causes impetigo and erysipelas rather than the chronic bilateral commissural fissuring described.

Note: Always ask WHY the commissures are macerated, because treating the fungus without the cause guarantees recurrence. Look for reduced occlusal vertical dimension (an old, worn denture is the classic culprit), denture stomatitis providing a reservoir on the palate, iron, folate or B12 deficiency, diabetes, and immunosuppression. Treat with a topical antifungal plus a barrier, and correct the underlying factor.