Last Minute revision of Dermatology

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 .

Last Minute revision of Dermatology
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