Fungal infection caused by a related group of yeasts. Manifestations may be localized to the skin or rarely systemic and life-threatening. Predisposing factors include diabetes mellitus, cellular immune deficiencies, and HIV. Frequently involved sites include the oral cavity, chronically wet macerated areas, around nails, intertriginous areas. Candidiasis is diagnosed by clinical pattern and demonstration of yeast on KOH preparation or culture.
Skin fungus, may involve any area of body; due to infection of stratum corneum, nail plate, or hair. Appearance may vary from mild scaliness to florid inflammatory dermatitis. Common sites of infection include the foot (tinea pedis), nails (tinea unguium), groin (tinea cruris), or scalp (tinea capitis). Classic lesion of tinea corporis (“ringworm”) is an erythematous papulosquamous patch, often with central clearing and scale along peripheral advancing border. Hyphae are often seen on KOH preparation, although tinea capitis and tinea corporis may require culture or biopsy.
Depends on affected site and type of infection
Erysipelas is superficial cellulitis, most commonly on face, characterized by a bright red, sharply demarcated, intensely painful, warm plaque. Because of superficial location of infection and associated edema, surface of plaque may exhibit a peau d’orange (orange peel) appearance. It is most commonly due to infection with group A alpha-hemolytic streptococci, occurring at sites of trauma or other breaks in skin.
Herpes simplex is characterized by grouped vesicles on an erythematous base that progress to erosions; often secondarily infected with staphylococci or streptococci. It frequently involves mucocutaneous surfaces around the oral cavity, genitals, or anus. Tzanck preparation of an unroofed early vesicle reveals multinuclear giant cells.
Eruption of grouped vesicles on an erythematous base usually limited to a single dermatome (“shingles”). Disseminated lesions can also occur, especially in immunocompromised patients. Tzanck preparation reveals multinucleate giant cells; indistinguishable from herpes simplex except by culture. Post herpetic neuralgia, lasting months to years, may occur, especially in the elderly.
Impetigo is a superficial infection of skin secondary to either S. aureus or group A alpha-hemolytic streptococci. The primary lesion is a superficial pustule that ruptures and forms a “honey-colored” crust. Tense bullae are associated with S. aureus infections (bullous impetigo). Lesions may occur anywhere but commonly involve the face.
Molluscum contagiosum is a common cutaneous infection caused by a pox virus. Clinically, lesions are multiple, small (1-3 mm) translucent papules which often look like fluid-filled vesicles but are in fact solid. Individual lesions may have central umbilication. They can occur at anybody site including the genitalia. Transmission is by direct contact. Occasionally lesions may be up to 1 cm in diameter ('giant molluscum'). They are said to be more extensive in children with atopic eczema, which may just reflect that scratching aids their spread.
Scabies is an intensely itchy rash caused by the mite Sarcoptes scabiei. It is most common in children and young adults but can affect any age group. It is commoner with social overcrowding. Scabies is spread by prolonged close contact such as within households or institutions, and by sexual contact. It presents clinically with itchy red papules (or occasionally vesicles and pustules), which can occur anywhere in the skin but rarely on the face, except in neonates. Sites of predilection are between the web spaces of the fingers and toes, on the palms and soles, around the wrists and axillae, on the male genitalia, and around the nipples and umbilicus. The pathognomonic sign is of linear or curved skin burrows but these are not always present. The pruritus is normally worse at night. Excoriations and secondary bacterial infection may complicate the rash.
Scabies can be confirmed by taking skin scrapings of a lesion and examining a potassium hydroxide preparation for the mite and/or its eggs by microscopy.
Warts are cutaneous lesions caused by human papilloma viruses (HPVs). They are typically dome-shaped lesions with irregular filamentous surface. Warts have propensity for the face, arms, and legs; often spread by shaving. HPVs are also associated with genital or perianal lesions and play a role in the development of cancer of the uterine cervix and external genitalia in females.