Candidiasis — Viva

Q1: Definition and classification (2 min)

Define candidiasis and explain how it is classified for clinical and examination purposes. What is the difference between superficial (cutaneous and mucocutaneous) candidiasis and invasive candidiasis?

Expected points

• Candidiasis is a superficial fungal infection caused by dimorphic yeasts of the genus Candida; C. albicans is the most common species, but non-albicans species are increasing.
• Superficial disease affects skin, mucosa and peri-ungual tissues; invasive disease denotes candidemia or deep organ infection.
• Anatomical classification: cutaneous (intertrigo, napkin/diaper dermatitis, paronychia), mucosal (oral thrush, angular cheilitis, vulvovaginal candidiasis, balanitis), and chronic mucocutaneous candidiasis (CMC) from defective Th17 immunity.

Q2: Risk factors and pathophysiology (2 min)

What local and systemic factors predispose to candidiasis? How does Candida cause disease?

Expected points

• Local factors: moisture, occlusion, maceration, skin folds, napkin environment, wet work, dentures, synthetic clothing.
• Systemic factors: diabetes mellitus, HIV/AIDS (especially CD4 < 200 cells per microlitre), broad-spectrum antibiotics, inhaled/systemic corticosteroids, immunosuppression, pregnancy, obesity, nutritional deficiencies (iron, folate, B12, zinc).
• Pathophysiology: yeast-to-hypha morphological switch, adhesins, secreted aspartyl proteinases, phospholipases, biofilm formation, and Th17-dependent host defence. STAT1 gain-of-function impairs IL-17 responses and causes CMC.

Q3: Clinical presentation and differential diagnosis (3 min)

Describe the clinical features of candidal intertrigo, oral thrush and vulvovaginal candidiasis. How would you distinguish candidiasis from other conditions?

Expected points

• Intertrigo: bright-red, moist, macerated fold plaque with satellite pustules; common in groin, axillae, inframammary folds.
• Oral thrush: pseudomembranous white plaques removable with a spatula, erythematous base; angular cheilitis affects commissures.
• VVC: pruritus, soreness, cottage-cheese discharge, vulvar erythema; recurrent VVC is defined as four or more symptomatic episodes per year.
• Differentials: tinea corporis/cruris (septate hyphae, no satellite pustules), inverse psoriasis (well-demarcated, shiny, no pustules), erythrasma (coral-red fluorescence), seborrhoeic dermatitis, contact/irritant dermatitis, bacterial intertrigo, Hailey-Hailey disease.
• KOH microscopy is the key distinguishing test.

Q4: Investigations and management (3 min)

How do you diagnose candidiasis? Outline the stepwise management of a patient with cutaneous and oral candidiasis.

Expected points

• Investigations: KOH microscopy showing budding yeasts and pseudohyphae; culture and antifungal susceptibility testing for recurrent, severe, atypical or non-albicans disease; blood cultures for invasive disease; endoscopy for suspected oesophageal candidiasis; screening for diabetes and HIV when appropriate.
• General measures: dry folds, loose cotton clothing, weight reduction, glycaemic control, avoid unnecessary antibiotics, denture hygiene, wet-work avoidance for paronychia.
• Topical therapy: nystatin or azoles (clotrimazole, miconazole, ketoconazole) for 1-2 weeks; oral nystatin/miconazole gel for thrush.
• Oral therapy: fluconazole 150 mg single dose for uncomplicated VVC; 100-200 mg daily for 7-14 days for oral/mucosal disease; 150 mg weekly for 6 months for recurrent VVC suppressive therapy; itraconazole for chronic paronychia; echinocandins for invasive candidiasis.^[5]
• Chronic mucocutaneous candidiasis: long-term systemic azoles, investigation for immune defects, consider ruxolitinib for STAT1 gain-of-function under specialist care.

Q5: Special situations and red flags (2 min)

When should you escalate care or investigate for underlying disease? Mention Candida auris.

Expected points

• Severe or recurrent oral candidiasis in an adult without local risk factors: test for HIV and diabetes.
• Recurrent VVC: culture to exclude non-albicans species, screen for diabetes, consider suppressive therapy.
• Candidemia or invasive candidiasis: echinocandin first-line, remove infected central lines, source control, ophthalmology review.
• Chronic mucocutaneous candidiasis from infancy: investigate STAT1, AIRE/APECED, IL-17 pathway defects; screen for endocrine autoimmunity.
• Candida auris: multidrug-resistant, outbreak-associated, requires strict infection control, species identification and susceptibility-guided therapy; notify public-health authorities.
• Pregnancy: avoid oral fluconazole; use topical imidazoles for VVC.