Superficial Candida infection of moist intertriginous skin, diaper area, and nail folds — beefy-red plaques with satellite pustules.
Also known as: candidiasis, candida intertrigo, diaper candidiasis, thrush, paronychia (candidal), candidal balanitis
Overview
Superficial infection of skin or mucous membranes by Candida species (most commonly C. albicans), favoring warm moist sites such as intertriginous folds, diaper area, perlèche (angles of mouth), genital mucosa, and chronically wet hands/nail folds.
Epidemiology
Very common across all ages. Peaks in infants (diaper area), elderly with incontinence, and immunosuppressed patients. Vulvovaginal candidiasis affects ~75% of women at least once in their lifetime.
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Question 1DermatologyMedium
A 7-month-old infant is brought in for a diaper rash that has persisted for 10 days despite frequent diaper changes and a zinc oxide barrier paste. He recently finished a course of oral amoxicillin for otitis media. On exam, there are beefy-red, moist, confluent plaques over the perineum and buttocks that extend deep into the inguinal skin folds, with a peripheral collarette of scale and scattered satellite pustules at the margins. Which of the following is the most likely diagnosis?
ABullous impetigo
BInverse psoriasis
CIrritant dermatitis
DCandida intertrigo
ESeborrheic eczema
Reveal answer & full explanation
Correct answer: D — Candida intertrigo
ABullous impetigo
BInverse psoriasis
CIrritant dermatitis
DCandida intertrigo✓
ESeborrheic eczema
Why Candida intertrigo is correct
Candidal intertrigo produces beefy-red, moist plaques that INVOLVE the inguinal skin folds, with satellite pustules/papules and a peripheral collarette of scale — the single best distinguishing feature.
Recent broad-spectrum antibiotics (amoxicillin) and the warm, occluded, macerated diaper environment are classic risk factors that allow the commensal yeast to undergo hyphal transition and invade.
Failure to improve on barrier paste and frequent changes points away from a simple irritant process; KOH would show budding yeast with pseudohyphae, and treatment is a topical antifungal (nystatin or clotrimazole) with each diaper change.
Why the others are wrong
Irritant dermatitis — irritant diaper dermatitis is caused by urine/feces contact on convex surfaces; it SPARES the inguinal folds and lacks satellite pustules, and it should respond to barrier paste and frequent changes.
Seborrheic eczema — presents with greasy yellow scale and typically also involves the scalp, face, and other flexures; it does not produce satellite pustules.
Inverse psoriasis — gives sharply demarcated, smooth red plaques in folds without satellite pustules, usually with a personal or family history of psoriasis.
Bullous impetigo — the collarette of scale and pustules can suggest it, because ruptured Staphylococcus aureus bullae leave a rim of scale around shiny erosions, but bullous impetigo produces flaccid bullae and discrete erosions rather than beefy-red, confluent plaques filling the inguinal folds with satellite pustules after antibiotic exposure.
Question 2DermatologyMedium
A 58-year-old woman with poorly controlled type 2 diabetes presents with a tender, beefy-red moist rash in both inframammary folds. Examination shows confluent erythematous plaques with a peripheral collarette of scale and several small pustules studding the surrounding skin just beyond the plaque edge. A scraping is taken from one of the pustules for potassium hydroxide (KOH) microscopy. Which of the following microscopic findings would best support the most likely diagnosis?
AKeratinocytes with no fungal elements
BLong, branching septate hyphae crossing cells
CShort hyphae with rounded spore clusters
DBudding yeasts with attached pseudohyphae
EBroad-based budding thick-walled yeast cells
Reveal answer & full explanation
Correct answer: D — Budding yeasts with attached pseudohyphae
AKeratinocytes with no fungal elements
BLong, branching septate hyphae crossing cells
CShort hyphae with rounded spore clusters
DBudding yeasts with attached pseudohyphae✓
EBroad-based budding thick-walled yeast cells
Why Budding yeasts with attached pseudohyphae is correct
A beefy-red intertriginous plaque with a peripheral collarette of scale and satellite pustules in a moist fold of a poorly controlled diabetic is classic cutaneous candidiasis (intertrigo).
KOH microscopy of Candida shows budding yeasts (blastoconidia) together with pseudohyphae, the finding that reflects the yeast-to-hyphal transition driving tissue invasion.
Diagnosis is usually clinical; KOH is the confirmatory bedside test, and fungal culture is reserved for refractory disease or species identification.
Why the others are wrong
Long, branching septate hyphae crossing cells - points to a dermatophyte such as tinea cruris, which shows a sharp scaly advancing border with central clearing, spares the scrotum, and lacks satellite pustules in the fold.
Short hyphae with rounded spore clusters - the spaghetti-and-meatballs pattern of tinea (pityriasis) versicolor from Malassezia, which causes hypo- or hyperpigmented macules on the trunk, not a satellite-pustule intertrigo.
Broad-based budding thick-walled yeast cells - the tissue form of Blastomyces dermatitidis, a dimorphic fungus endemic to the Ohio and Mississippi River valleys and Great Lakes region; its skin lesions (usually spread from a pulmonary focus) are verrucous or ulcerated plaques with heaped borders, not a moist satellite-pustule intertrigo, and it forms no pseudohyphae.
Keratinocytes with no fungal elements - a negative KOH is expected in erythrasma, a Corynebacterium minutissimum infection that also favors the skin folds of people with diabetes, but erythrasma forms well-demarcated, red-brown, finely scaling patches without satellite pustules and fluoresces coral-red under Wood's lamp; a beefy-red fold plaque with satellite pustules is candidal intertrigo, which shows budding yeasts with pseudohyphae.
Additional high-yield points
Septate hyphae with acute-angle (about 45 degree) branching is the classic Aspergillus descriptor in tissue, not a dermatophyte clue; dermatophyte KOH shows long, branching septate hyphae, often with arthroconidia.
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Topical corticosteroids (intertrigo) or inhaled corticosteroids (oral thrush)
Frequent wet work (paronychia, hand candidiasis)
Iron deficiency, hypothyroidism, hypoparathyroidism (chronic mucocutaneous candidiasis)
Pathophysiology
Candida is a commensal in oral, GI, and vaginal flora. Disruption of skin barrier, mucosal microbiome, or local/systemic immunity allows yeast-to-hyphal transition and tissue invasion. Inflammatory response produces erythema, satellite pustules, and pseudomembrane formation on mucosa.
Clinical presentation
Symptoms
Burning, itching, soreness in affected area
Vulvovaginal: thick white 'cottage cheese' discharge, pruritus, dyspareunia
Oral: white plaques that scrape off (pseudomembranous), painful red atrophic mucosa (erythematous/atrophic), or angular cheilitis (perlèche)
Paronychia: tender swollen erythematous nail fold, chronic
Signs / physical exam
Intertrigo: beefy-red erythematous moist plaques with peripheral collarette of scale and satellite pustules/papules — axillae, inframammary, inguinal, abdominal panniculus, intergluteal cleft
Diaper candidiasis: beefy-red plaques INVOLVING inguinal folds with satellite pustules (vs irritant diaper dermatitis which spares folds)
Oral thrush: white curd-like plaques that scrape off, leaving erythematous base; perlèche (angular cheilitis); median rhomboid glossitis
Vulvovaginal: erythema, edema, fissures, thick white discharge adherent to walls
Candidal balanitis: erythematous papules and pustules on glans with white exudate
Chronic paronychia: erythematous swollen proximal nail fold, loss of cuticle, secondary nail dystrophy
Classic findings
Beefy-red plaque with satellite pustules in skin folds; INVOLVES skin folds (unlike irritant or tinea); 'cottage cheese' vaginal discharge.
Cutaneous candidiasis variants and first-line therapy.
Treatment
First-line
Cutaneous intertrigo: topical antifungal — nystatin cream/ointment, clotrimazole 1%, miconazole 2%, ketoconazole 2% — BID until clear plus 1 week; keep area DRY (absorbent powder, hair dryer on cool, breathable fabrics, weight loss for chronic intertrigo)
Diaper candidiasis: nystatin or clotrimazole ointment with each diaper change; frequent diaper changes, air time, barrier paste (zinc oxide)
Oral thrush: nystatin suspension 4-6 mL swish-and-swallow QID × 7-14 days, OR clotrimazole troches 10 mg 5x/day, OR oral fluconazole 100-200 mg daily × 7-14 days (for moderate-severe disease)
Vulvovaginal (uncomplicated): single dose oral fluconazole 150 mg OR topical azole (clotrimazole, miconazole) intravaginal 1-7 days
Vulvovaginal (severe): fluconazole 150 mg × 2 doses 72 h apart, or topical azole × 7-14 days; vulvovaginal (recurrent, ≥3 episodes in <1 year): induction fluconazole 150 mg every 72 h × 3 doses (or topical azole × 7-14 days), then maintenance fluconazole 150 mg weekly × 6 months
Candidal balanitis: topical azole (clotrimazole or miconazole); treat a sex partner only if symptomatic; check glucose if recurrent; circumcision occasionally for refractory disease
Chronic paronychia: keep hands dry, avoid wet work, topical antifungal + low-potency steroid; oral fluconazole 150 mg weekly for severe
Esophageal / immunocompromised
Oral fluconazole 200-400 mg daily × 14-21 days
Echinocandin (caspofungin, micafungin) or amphotericin B for resistant species or systemic candidiasis
Address underlying immunosuppression
Chronic mucocutaneous candidiasis
Long-term oral azole therapy
Evaluate for autoimmune polyendocrine syndrome type 1 (APECED), STAT1 gain-of-function mutations, HIV
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