Bacterial, Viral, Fungal, and Parasitic Skin Infections

Vocabulary flashcards covering bacterial, viral, fungal, and parasitic skin conditions, including clinical presentation, diagnosis, key terminology, and management.

Impetigo

An acute, contagious superficial skin infection caused primarily by Staphylococcus aureus (50\text{--}70\text{\textpercent}) or Streptococcus pyogenes, presenting with erythematous macules, vesicles, and classic "honey colored crust" (or bullae indicating MRSA).

Folliculitis

An infection of the upper portion of the hair follicle, most commonly caused by Staph aureus, presenting as a papule or pustule confined to the hair follicle with surrounding erythema.

Hot Tub Folliculitis

A follicular infection caused by Pseudomonas, presenting as multiple erythematous pustules on the trunk usually $3$ days after exposure to a hot tub, typically sparing the bathing suit area.

Erysipelas

A Group A streptococcal infection involving the superficial dermal lymphatics, characterized by painful localized redness, heat, swelling, and a raised, well-demarcated indurated border.

Cellulitis

An acute spreading infection of the dermal and subcutaneous tissues caused by Staph aureus or Group A Strep, manifesting as a red, hot, edematous, shiny, tender plaque with irregular, slightly elevated borders.

Acute Paronychia

An acute infection of the lateral or proximal nail fold associated with a break in the epidermis (e.g., hangnail or trauma), presenting with pain, erythema, swelling, and potential abscess formation.

Chronic Paronychia

Erythema and swelling of the periungual tissue lasting over $6$ weeks, characterized by tissue retraction, loss of the cuticle, and separation of the nail plate from the proximal nail fold.

Tzanck Smear

A bedside diagnostic smear used in suspected viral infections that yields "Multinucleated Giant Cells" in cases of herpes simplex virus.

Herpes Zoster

Infection caused by reactivation of latent Varicella Zoster Virus in sensory nerve root ganglion cells, presenting as painful erythematous papules, vesicles, and crusted lesions in a unilateral dermatomal distribution.

Ophthalmic Zoster

A serious complication of herpes zoster involving the 5th cranial nerve; involvement of the tip of the nose indicates ocular involvement 76\text{\textpercent} of the time and requires an immediate ophthalmology consult.

Shingrix

The recombinant shingles vaccine recommended as a $2$-dose series for all adults aged $>50$ years to prevent herpes zoster.

Verruca Vulgaris

Common cutaneous warts occurring on hands, fingers, palms, lips, or tongue, presenting as firm, elevated, rough papules measuring $1\text{--}10\text{ mm}$ with a grayish rough surface.

Verruca Plana

Flat warts seen in children and young adults, presenting as $2\text{--}4\text{ mm}$ flat-topped pink or brown papules clustered on the forehead, cheeks, nose, neck, or knees.

Verruca Plantaris

Plantar warts located at pressure points over the balls of the feet, featuring a soft core surrounded by a thick, firm keratinous ring.

Mosaic Wart

A large hyperkeratotic lesion formed on the foot when multiple individual verruca plantaris lesions fuse together.

Condyloma Acuminata

Visible anogenital warts caused by human papillomavirus (mucocutaneous types), presenting as soft, pink, cauliflower-like papules.

Acetowhitening

A clinical diagnostic maneuver in which application of acetic acid causes condyloma acuminata lesions to turn white and become more clearly visible.

Molluscum Contagiosum

A self-limited epidermal viral infection caused by a poxvirus, presenting as smooth, firm, dome-shaped pearly papules with central umbilication.

Tinea Corporis

Dermatophyte fungal infection of the trunk, legs, arms, or neck, presenting as sharply demarcated plaques with peripheral enlargement and central clearing.

Tinea Cruris

Fungal infection of the groin, pubic region, and inner thighs, presenting as large, scaling, dull red, well-demarcated plaques with central clearing.

Tinea Pedis (Moccasin type)

A variant of athlete's foot characterized by well-demarcated erythema and fine white scaling along the soles and sides of the feet, classically described in a "2 foot one hand" distribution.

Tinea Capitis

Fungal scalp infection common in children aged $6\text{--}10$ years, presenting with alopecia, broken hair shafts, light gray scaling, and sharp borders.

Kerion

An inflammatory hypersensitivity reaction to tinea capitis resulting in a boggy, erythematous, oozing scalp plaque that can cause secondary bacterial infection and permanent scarring alopecia.

Onychomycosis

Fungal infection of the nail plate (tinea unguium) leading to thickening and discoloration, most commonly affecting the distal and lateral borders of the 1st and 5th toenails.

Tinea Versicolor

Fungal infection/overgrowth of Pityrosporum ovale causing sharply marginated, round-to-oval macules with fine scale (white, light brown, or erythematous) that demonstrate a "spaghetti and meatballs" appearance on KOH prep.

Intertrigo

Candida skin fold infection presenting as moist, red/brown, beefy patches located in intertriginous areas like the groin, axillae, or under breasts.

Diaper Dermatitis (Candida)

Candidal infection in infants within the diaper distribution, characterized by "beefy" red confluent plaques in the skin folds accompanied by distinct "satellite lesions".

Pediculosis Humanus Capitis

Head lice infestation caused by $1\text{--}3\text{ mm}$ long parasites that deposit opalescent eggs (nits) measuring less than $1\text{ mm}$ on hair shafts.

Malathion (Ovide)

A prescription topical pediculicide applied overnight to treat lice; it is flammable (requiring heat avoidance after washing) and contraindicated in children under $6$ years old.

Scabies

A contagious skin infestation caused by the human itch mite Sarcoptes scabiei, producing severe nocturnal pruritus and an eczematous papular eruption with linear burrows.

Scabies Prep

A diagnostic microscopic exam using oil immersion to identify Sarcoptes scabiei mites, eggs, larvae, or scybala (feces) scraped from skin lesions.

Norwegian Crusted Scabies

A severe hyperkeratotic form of scabies harboring up to $2$ million live mites, seen predominantly in immunocompromised or neurologically impaired patients.