USMLE Step 2 (Fach) / Dermatology (Lektion)
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Step 2 CK
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- Atopic dermatitis (eczema) Epidemiology:- About 10-15% of all children are affected- Onset of symptoms usually occurs between 3-6 months of age- Disease often improves with age Etiology:- Genetics (polygenic inheritance): Approx. ...
- Erythema toxicum neonatorum Benign eruption that typically begins 1-3 days after delivery and resembles ezcema, presenting with red papules, pustules, and/or vesicles with surrrounding erythematous halos. - ↑ eosinophils are ...
- Contact dermatitis A type IV hypersensitivity reaction that results from contact with an allergen to which the patient has previously been exposed and sensitized. Etiology:- Poison ivy, poison oak, poison sumac (urushiol-induced ...
- Seborrheic dermatitis A common chronic inflammatory skin disease that may be caused by hypersensitivity reaction to Malassezia furfur, a generally harmless yeast found in sebum and hair follicles. It has a predilection for ...
- Stasis dermatitis Lower extremity dermatitis due to venous hypertension forcing blood from the deep to the superficial venous system. Venous hypertension is often a result of venous valve incompetence or flow obstruction. ...
- Psoriasis Epidemiology:- Prevalence: ∼ 2% of the white population- Age of onset: 20-40 years Trigger factors:- Infectious: Infections caused by group A streptococci, staphylococcus, HIV- Mechanical irritation- ...
- Urticaria (Hives) Results from the release of histamine and prostaglandins from mast cells in a type I hypersensitivity response. It is characterized by superficial, intense erythema and edema in a localized area. Can ...
- Erythema multiforme A rare, acute hypersensitivity reaction most commonly triggered by herpes simplex virus (HSV) infections. Etiology:- Infections (most common): herpes simplex virus (HSV), Mycoplasma pneumoniae, and fungal ...
- Stevens-Johnson syndrome/Toxic epidermal necrolysis ... SJS and TEN constitute two different points on the spectrum of life-threatening exfoliative mucocutaneous diseases that are often caused by a drug-induced immunologic reaction.< 10% = SJS10-30% = SJS/TEN ...
- Erythema nodosum An inflammation of subcutaneous fat caused by a delayed hypersensitivity reaction. Epidemiology:- Sex: F > M- Peak incidence: 18-34 years Etiology: - Idiopathic (most common)- Infection (e.g. streptococcal ...
- Bullous pemphigoid Epidemiology:- Peak incidence: > 60 years of age- Most common bullous autoimmune disease Etiology: Autoantibodies directed against hemidesmosomes Clinical features:- Prodromal phase characterized by ...
- Dermatitis herpetiformis Epidemiology:- Peak incidence: 15-40 years- ♂ > ♀ Etiology:- Most likely genetic predisposition to autoimmune reaction (associated with HLA-DR3 and HLA-DQ2)- Associated with celiac disease; sensitivity ...
- Molluscum contagiosum A poxvirus infection that is most common in young children and in AIDS patients. It is spread by direct skin-to-skin contact (sport, sex) or sharing infected clothing or towels. Risk factors: immunosuppression, ...
- Verrucae (warts) Hyperkeratosis and hyperplasia of epidermis commonly caused by human papillomavirus. Epidemiology: more frequent in children and young adults Etiology: Human papillomavirus infection (HPV) 1, 2, 4; transmitted ...
- Impetigo Local infection of the epidermis that primarily occurs in children and is caused by both group A streptococcal and staphylococcal orgnaisms. Epidemiology:- Age: primarily affects children (especially ...
- Folliculitis Inflammation and/or infection of a hair follicle. Typically caused by infection with Staphylococcus, Streptococcus, and gram - bacteria. Occasionally can be caused by yeast such as Candida albicans or ...
- Acne vulgaris Etiology:- Genetic predisposition- Hormonal factors: Sebum production, menstrual cycle- Follicular hyperkeratosis- Bacterial colonization with Cutibacterium acnes (formerly known as Propionibacterium ...
- Pilonidal cyst A skin condition caused by local inflammation of the superior midline gluteal cleft, which may progress to a local abscess or fistula. Epidemiology:- Sex: ♂ > ♀ (∼ 3:1)- Peak incidence: 15-25 years ...
- Tinea versicolor Epidemiology:- Occurs worldwide, with a higher incidence in tropical climates- More prevalent in healthy individuals of 15-24 years of age Pathogen: Malassezia globosa and furfur (part of normal skin ...
- Candidiasis Pathogen: Candida albicans (most common) Risk factors:- Immunosuppression is the main risk factor for infection: HIV, diabetes mellitus, certain patient groups (e.g., ICU, transplant patients, surgical ...
- Dermatophyte infections Dermatophyte infections, also known as tinea, are the most common fungal infections of the skin, hair, and nails. Pathogen: Trichophyton (most common), Microsporum, and Epidermophyton Risk factors:- Diabetes ...
- Lice Lice live off blood and on specific parts of the body, depending on their species (head lice, body lice, public lice). Lice are spread through body contact or by the sharing of bedclothes and other garments ...
- Scabies Scabies is a parasitic skin infestation caused by the Sarcoptes scabiei mite. Clinical features:- Incubation period: approximately 3-6 weeks following infestation- Intense pruritus at night - Burning ...
- Acanthosis nigricans A condition in which the skin in the intertriginous zones (neck folds, genitals, axillae) is hyperkeratotic and hyperpigmented with a velvet appearance. Etiology:- Endocrinal: diabetes mellitus type 2, ...
- Lichen planus A self-limited, recurrent, or chronic inflammatory disease affecting the skin, oral mucosa, and genitalia.- Associated with HCV infection.- Drug-induced: ACE-inhibitors, thiazides, furosemide, beta-blockers ...
- Rosacea Epidemiology:- Sex: F > M- Age range: 30-60 years Etiology: The cause of rosacea is not entirely understood, but is especially associated with triggers that increase body temperature. Trigger factors:- ...
- Pityriasis rosea An acute dermatitis of unknown etiology that has been hypothesized to represent a reaction to a viral infection with human herpesvirus (HHV) 7 because it tends to occur in mini-epidemics among young adults. ...
- Vitiligo Vitiligo is a common skin condition in which a patchy loss of epidermal melanocytes results in depigmentation. Epidemiology:- Prevalence: 1-2% of the general population- Peak incidence: 20-30 years; can ...
- Eyelid lesion Xanthelasma: Soft and yellow plaques seen on the medial aspects of the eyelids bilaterally, associated with hyperlipidemia and 1° biliary cirrhosis. Hordeolum: Painful acute eyelid gland infection (stye), ...
- Seborrheic keratosis Benign growths of immature keratinocytes Epidemiology: most common benign skin tumor in the elderly population Etiology: incompletely understood, genetic predisposition Clinical features:- Multiple darkly ...
- Actinic keratosis A UV-induced precancerous skin lesion that may progress to skin cancer. Epidemiology: occurs especially in individuals with light skin who are over the age of 50 Etiology: sun exposure (e.g., from working ...
- Cutaneous squamous cell carcinoma Epidemiology: Second most common form of skin cancer after basal cell carcinoma Risk factors:- Sun exposure (especially among fair-skinned individuals)- Exposure to ionizing radiation- Exposure to chemical ...
- Basal cell carinoma Epidemiology:- Most common malignant skin tumor- Sex: ♂ > ♀ (∼ 2:1) Etiology:- Sun exposure- Skin types I and II (people with light complexions, red hair, and who sunburn easily)- Nevoid basal-cell ...
- Melanoma The most common life-threatening dermatologic disease. Etiology:- UV radiation exposure- Light skin- Numerous nevi, giant congenital nevi, or inherited skin conditions (e.g., dysplastic nevus syndrome, ...
- Kaposi sarcoma A vascular proliferative disease that has been attributed to a herpesvirus HHV-8. History/PE:- Presents with multiple red to violaceous macules, papules, or nodules that can progress to plaques on the ...
- Mycosis fungoides Chronic, low-grade, malignant, CD4+ T-cell non-Hodgkin lymphoma that presents on the skin. Epidemiology: - Uncommon: only 4% of non-Hodgkin lymphoma cases- Age: mostly middle-aged or elderly patients- ...
- Cherry angiomas (hemangiomas) Epidemiology: incidence increases with age (most common acquired cutaneous vascular anomaly) Pathophysiology: proliferation of dilated mature capillaries Clinical features:- Bright cherry red, dome-shaped ...
- Keratocanthoma Low-grade tumor, more common in the elderly - Associated with Muir-Torre syndrome (variant of Lynch syndrome) Characteristic features:- Rapid growth (within 2-3 months) in areas of skin exposed to the ...
- Pemphigus vulgaris Epidemiology: - Peak incidence: 40-60 years of age Etiology:- IgG antibodies directed against desmoglein 3 and desmoglein 1 in desmosomes - Exacerbating factors: drugs, viruses, UV radiation, diet ...
- Porphyria cutanea tarda Epidemiology:- Most common porphyria- Peak incidence: 40-70 years- Sex: M > F Etiology: Defective uroporphyrinogen III decarboxylase (UROD)- Type I: acquired insufficiency of UROD in the context of hepatic ...
- Alopecia Classification:1. Cicatricial (scarring) alopecia- Brocq pseudopelade→ Seen in women 30-55 years of age→ Irregular areas of irreversible hair loss, which become scarred areas at a later stage- Lichen ...
- Telogen effluvium The telogen (resting) phase of hair growth predominates → premature shedding of the resting hair follicles → diffuse, nonscarring hair loss Triggers:- Severe illness, fever, surgery- Pregnancy, childbirth- ...
- Alopecia areata Nonscarring hair loss in well demarcated patches due to immune mediated inflammation of hair follicles Epidemiology:- Prevalence: 1 in 1000 people- Age: mostly in people < 30 years- Sex: ♂ = ♀ Etiology:- ...
- Burns 1st degree (superficial burn): Superficial layers of the epidermis- Pain- Erythema- Swelling- The burn wound blanches on applying pressure and refills rapidly- Healing within 3-6 days without scarring ...
- Staphylococcal scaled skin syndrome (SSSS) Pathogen: Staphylococcus aureus strains that produce exfoliative toxins that cleave desmoglein-1 in the granular layer of the epidermis, thereby disrupting keratinocyte attachments. Clinical features:- Fever, ...
- Methotrexate Folic acid antagonist (antimetabolite) → purine nucleotide and thereby ↓ DNA synthesis Clinical use:- Treatment of severe psoriasis and rheumatoid arthritis- In neoplastic diseases like gestational ...
- Sézary syndrome Cutaneous T-cell lymphoma with leukemic dissemination of mutated T cells.Can be an advanced form of mycosis fungoides or arise de novo. Characteristic triad of symptoms:1. Systemic skin lesions- Erythroderma ...
- Hidradenitis suppurativa Chronic inflammatory condition that involves recurrent occlusion of hair follicles in intertriginous regions (e.g., groin, axilla). Epidemiology: Women aged 20-40 Risk factors: obesity, smoking, family ...
- Dermatofibroma Fibroblast proliferation resulting in small, fibrous benign dermal growth. Epidemiology: ♀ > ♂ Etiology: sometimes related to insect bites or trauma, may have unknown cause Clinical features:- Asymptomatic- ...
- Pyogenic granuloma Benign vascular tumor Etiology: cause unknown, associated with trauma and pregnancy Clinical features:- Soft, round, bright red tumor that bleeds easily- Localization: usually develops at a site of ...