Important topics to revise in dermatology
Atopic eczematous dermatitis | Pruritic eruption, commonly on skin flexures. Often associated with other atopic diseases (asthma, allergic rhinitis, food allergies). |
Contact dermatitis | Type IV hypersensitivity reaction that follows exposure to allergen. Lesions occur at site of contact |
Urticaria | Hives. Pruritic wheals that form after mast cell degranulation. Characterized by superficial dermal edema and lymphatic channel dilation. Dermatographism +ve. Treatment: Antihistamines. |
Acne vulgaris | Grade I: comedones +- few papules Grade II: comedones + papules Grade III: comedones + papules + pustules + scars, the most common type Grade IV – predominantly nodules and scars Treatment: Topical benozyl peroxide, clindamycin, retinoids. Oral: Azithromycin, doxycycline, minocycline, retinoids. |
Verrucae | · Warts; caused by HPV. · Soft, tan-colored, cauliflower-like papules . · Epidermal hyperplasia, hyperkeratosis, koilocytosis. · Condyloma acuminatum on genitals . |
Psoriasis | Papules and plaques with silvery scaling , especially on knees and elbows. pinpoint bleeding spots from exposure of dermal papillae when scales are scraped off. Can be associated with nail pitting and psoriatic arthritis. |
Rosacea | Inflammatory facial skin disorder characterized by erythematous papules and pustules , but no comedones . May be associated with facial flushing in response to external stimuli (eg, alcohol, heat). Phymatous rosacea can cause rhinophyma (bulbous deformation of nose). |
Pityriasis rosea | “Herald patch” followed days later by other scaly erythematous plaques, often in a “Christmas tree” distribution on trunk . Multiple plaques with collarette scale. Self-resolving in 6–8 weeks. |
Pseudofolliculitis Barbae | Foreign body inflammatory facial skin disorder characterized by firm, hyperpigmented papules and pustules that are painful and pruritic. Located on cheeks, jawline, and neck . |
Sunburn | Acute cutaneous inflammatory reaction due to excessive UV irradiation. |
Melanocytic nevus | Common mole. Benign, but melanoma can arise in congenital or atypical moles. Intradermal nevi are papular . Junctional nevi are flat macules . |
Erythema nodosum |
Painful, raised inflammatory lesions of subcutaneous fat (panniculitis), usually on anterior shins. |
Seborrheic keratosis |
Flat, greasy, pigmented squamous epithelial proliferation with keratin-filled cysts (horn cysts). Looks “stuck on.” Lesions occur on head, trunk, and extremities . Leser-Trélat sign—sudden appearance of multiple seborrheic keratoses, indicating an underlying malignancy (eg, GI, lymphoid). |
Actinic keratosis |
Premalignant lesions caused by sun exposure. Small, rough, erythematous or brownish papules or plaques. |
Acanthosis nigricans |
Epidermal hyperplasia causing symmetric, hyperpigmented thickening of skin, especially in axilla or on neck . Associated with insulin resistance (eg, diabetes, obesity, Cushing syndrome), visceral malignancy (eg, gastric adenocarcinoma). |
Lichen planus |
Pruritic, Purple, Polygonal Planar Papules and Plaques are the 6 P’s of lichen Planus |
Pemphigus vulgaris |
Flaccid intraepidermal bullae caused by acantholysis (separation of keratinocytes, resembling a “row of tombstones”); oral mucosa is also involved. |
Bullous pemphygoid |
Tense blisters containing eosinophils affect skin but spare oral mucosa. |
Dermatitis herpetiformis |
Pruritic papules, vesicles, and bullae (often found on elbows) . |
Steven Johnson synd |
Presents with multiple types of lesions— macules, papules, vesicles, target lesions (look like targets with multiple rings and dusky center showing epithelial disruption) . |
Erythema multiforme |
Presents with multiple types of lesions— macules, papules, vesicles, target lesions (look like targets with multiple rings and dusky center showing epithelial disruption) |
Stevens-Johnson syndrome |
Characterized by fever, bullae formation and necrosis, sloughing of skin at dermal-epidermal junction, high mortality rate. Typically 2 mucous membranes are involved , and targetoid skin lesions may appear, as seen in erythema multiforme. |
Epithelial tumors |
Basal cell carcinoma : Waxy, pink, pearly nodules, commonly with telangiectasias, rolled borders, central crusting or ulceration . BCCs also appear as nonhealing ulcers with infiltrating growth or as a scaling plaque (superficial BCC).
Squamous cell carcinoma : Commonly appears on face , lower lip , ears, hands. Locally invasive, may spread to lymph nodes, and will rarely metastasize. Ulcerative red lesions with frequent scale.
Keratoacanthoma is a variant that grows rapidly (4–6 weeks) and may regress spontaneously over months.
Melanoma : Asymmetry, Border irregularity, Color variation, Diameter > 6 mm, and Evolution over time. At least 4 different types of melanoma, including superficial spreading , nodular , lentigo maligna, and acral lentiginous . |
Disorders of pigmentation and melanocytes |
Vitiligo : Localized loss of skin pigmentation .
Albinism : Congenital lack of pigmentation , May involve the eyes (ocular form) or both the eyes and skin (oculocutaneous form) .
Freckle : Small, tan to brown macule; darkens when exposed to sunlight .
Melasma ( chloasma ) : Mask-like hyperpigmentation of the cheeks .
Nevus : a flat macule or raised papule with symmetry, sharp borders , evenly distributed color, and small diameter(< 6 mm) |
Infectous disorders of Skin |
Impetigo : Very superficial skin infection , Highly contagious. Honeycolored crusting . Bullous impetigo has bullae and is usually caused by S aureus.
Erysipelas : Infection involving upper dermis and superficial lymphatics , Presents with well-defined demarcation between infected and normal skin .
Cellulitis : Acute, painful, spreading infection of deeper dermis and subcutaneous tissues.
Abscess : Collection of pus from a walled-off infection within deeper layers of skin.
Necrotizing fasciitis : Deeper tissue injury, usually from anaerobic bacteria or S pyogenes. Pain may be out of proportion to exam findings. Results in crepitus from methane and CO2 production. “Flesh-eating bacteria.” Causes bullae and a purple color to the skin .
Staphylococcal scalded skin syndrome : Characterized by fever and generalized erythematous rash with sloughing of the upper layers of the epidermis that heals completely .
Herpes : include herpes labialis, herpes genitalis, herpetic whitlow (finger).
Molluscum contagiosum : Umbilicated papules caused by a poxvirus.
Varicella zoster : Causes varicella (chickenpox) and zoster (shingles). Varicella presents with multiple crops of lesions in various stages from vesicles to crusts. Zoster is a reactivation of the virus in dermatomal distribution (unless it is disseminated).
Verruca : mentioned before .
Hairy leukoplakia : Irregular, white, painless plaques on lateral tongue that cannot be scraped off . |