Dermatology UWorld Qbank 2015
Terms in this set (57)
A 29-year-old female started to use new mascara several days ago and now has a pruritic facial skin rash. Exam reveals skin erythema, vesicles and oozing over the upper eyelids. What condition does she likely have?
Eczematous dermatitis: a term that encompasses a range of different condition clinically characterized by erythematous, papulovesicular, weeping, encrusted lesions that may evolve into thickened, scaly plaques; while still "wet" these lesion are prone to bacterial superinfection and can develop a yellow crust
Name the five distinct categories of eczematous dermatitis.
1. Allergic contact dermatitis; 2. Atopic dermatitis; 3. Drug-related eczematous dermatitis; 4. Photo-eczematous dermatitis; 5. Primary irritant dermatitis
How is acute eczematous dermatitis characterized histologically?
Spongiosis: epidermal accumulation of edematous fluid in the intercellular spaces
Describe the etiology of allergic contact dermatitis.
Antigens at the epidermal surface are selected by Langerhans cell and carried to the draining lymph nodes where they are presented to naïve CD4 T cells → CD4 T cells are activated and migrate to the skin → incite an inflammatory response within 24 hours of antigen re-exposure (cutaneous delayed hypersensitivity in the form of spongiotic dermatitis is the end result)
A 56-year-old man has multiple flat, well-circumscribed macules and patches of absent pigment, varying in size from a few to several centimeters. What is his likely condition?
What histological findings characterize vitiligo?
Loss of melanocytes and complete absence of melanin pigment
When does vitiligo most common develop?
Second or third decade of life; however the age of onset varies.
A 64-year-old man has small (< 1cm), scaly, erythematous lesions with sandpaper texture on his forehead. What are the likely lesions?
Actinic keratoses; result of chronic sun exposure
Name three characteristic light microscopy findings in actinic keratosis.
1. Hyperkeratosis (hyperplasia of the stratum corneum); 2. Parakeratosis (retention of nuclei in the stratum corneum); 3. Atypical keratinocytes (with pleomorphic nuclei and multiple mitosis)
Patients with actinic keratoses are at increased risk for developing what condition?
Squamous cell carcinoma (SCC); actinic keratoses do NOT invade the dermis and are considered premalignant lesion; a small percentage transform to invasive SCC, which is reflected by an increase in lesion size and thickness, dermal invasion and metastatic potential
What is the most common skin cancer?
Basal cell carcinoma (BCC); arises on sun-exposed areas and has a very low tendency to metastasize (in contrast to melanoma)
How does basal cell carinoma often present?
Pearly papules with central depression or ulceration; histologically, features nests of basaloid cells and peripheral palisading of nuclei
Light microscopy of a biopsy from a lesion on the upper eyelid of a 46-year-old woman shows multiple lipid-laden macrophages. Name the likely lesion.
Xanthelasma; these papules are typically yellow due to the location of the foam cells in the superficial dermis
Xanthelasmas are associated with what conditions?
Primary hyperlipidemia and secondary hyperlipidemia
Name two causes of secondary hyperlipidemia?
1. Obstructive biliary lesions; 2. Primary biliary cirrhosis
A 52-year-old woman has a 2-month history of oral lesions that cause pain with chewing and swallowing food. She thought they would have gone away. On examination, there are erosions of the buccal and gingival mucosa. There are several flaccid bullae with erosions scattered over her trunk. The blisters spread laterally with pressure, and traction on seemingly uninvolved skin produces blistering. What condition does she likely have?
Pemphigus valgaris; autoimmune bullous disease characterized by painful flaccid bullae and erosions of the skin and mucosal membranes; positive Nikolsky sign
Autoantibodies directed against what structure are present in pemphigus valgaris?
Desmosomes; specifically desmogleins 1 and 3 which disrupt cohesion of keratinocytes; biopsy of an active PV lesion will show intraepithelial cleavage with detached keratinocytes (acantholysis), retained keratinocytes along the basement membrane
A 44-year-old female has focal dimpling of the skin and inversion of the nipple of the right breast. Biopsy of the breast tissue underlying these changes demonstrates invasive carcinoma. What is responsible for her skin findings?
Suspensory ligament infiltration; nipple inversion is observed when the tumor invades the central region of the breast and skin retraction is identified when the cancer infiltrates the suspensory Cooper ligament
Name a circumstance in which pitting and thickening of the skin of the breast such that it adopts the appearance of an orange peel (peau d'orange) is seen.
Lymphatic drainage impeded by a breast tumor; peau d'orange is particularly common in patients with inflammatory breast cancer
Red blood cell extravastion into the skin or subcuraneous tissue results in the formation of petechiae, purpura and/or ecchymoses. These lesions do not completely blanch under pressure, unlike telangiectasias. How do you differentiate petechiae, purpura and ecchymoses?
Petechiae (<5mm), purpura (5mm to 1cm), ecchymoses (>1cm diameter)
A 31-year-old female has several subcutaneous bumps that seem to be attached to her Achilles tendons. What is the best initial test in this patient?
A 3-year-old boy has recurrent skin rashes. He develops an erythematous, itching rash on his cheeks, trunk, and arms about 5 or 6 times a year. The eruptions seem to be related to the consumption of certain foods. What is his likely condition?
Atopic dermatis (eczema); chronic inflammatory skin disorder triggered by various environmental factors such as ingestion of certain foods or exposure to certain environmental irritants; present with pruritus and erythematous, weeping/crusted papules and plaques that occur in response to certain environmental antigens
Atopic dermatitis (eczema) is associated with what other conditions?
Atopic disease, such as allergic rhinitis and asthma
A 54-year-old woman was diagnosed with right-sided breast carcinoma twelve years ago and was treated with radical mastectomy. Extensive axillary lymph node dissection performed at that time revealed no lymph node metastases. Post-operatively she developed chronic lymphedema. She now has multiple firm violaceous nodules on her right upper arm. What is the most likely etiology of her current skin lesion?
Angiosarcoma; chronic lymphedema is a risk factor for the development of cutaneous angiosarcoma, also known as Stewart-Treves syndrome; radical mastectomy with axillary lymph node dissection is a classic predisposing procedure
A 28-year-old male has bilateral skin lesions over his elbows. Biopsy reveals very thin stratum granulosum and prominent parakeratotic stratum corneum with occasional foci of neutrophil accumulation. What is the likely diagnosis?
Psoriasis; common chronic inflammatory skin disorder: 1-2% of US population; characterized by sharply demarcated salmon-colored rounded plaques covered with a loosely adherent, silvery scales
How is psoriasis characterized histologically?
Hyperparakeratosis, acanthosis (epidermal hyperplasia), elongation of the rete ridges, mitotic activity above the epidermal basal cell layer, reduced or absent stratum granulosum (right above stratum basale)
When a scale is removed from the plaque in psoriasis what is a common finding?
Pinpoint bleeding (Auspitz sign); thinning and dilated blood vessel in the epidermal cell layer superior to the dermal papillae is a cause
What histological finding with regards to neutrophils may be present in psoriasis?
Neurtophils may form spongiotic clusters in the superficial dermis and the parakeratotic stratum corneum (Munro microabscesses)
A 48-year-old man who recently immigrated to the US has a few well-defined, hypopigmented lesions on the skin of his lower extremities that have diminished sensation. After confirming the diagnosis of leprosy, the patient has intradermal injection of heat-killed Mycobacterium leprae. The injection causes the development of a large indurated nodule. What does this test indicate about the severity of his disease?
A positive lepromin skin test is present in patients with tuberculoid leprosy because they exhibit a strong CD4+ Th1 cell-mediated immune response to Mycobacterium leprae; Patients with lempromatous leprosy test negative due to their weak Th1 cell-mediated immune response; the disease is classified along a spectrum between tuberculoid (mild) to lepromatous (severe)
Name three cytokines associated with a Th1-mediated response that you would expect to be elevated in patients with tuberculoid leprosy.
IL-2, IFN-gamma, IL-12; this stong Th1-mediated response activates macrophages that kill M. leprae, thereby limiting disease extent; however, this localized inflammation damages the skin and cutaneous nerves, leading to the development of a small number of hypopigmented, well-demarcated plaques with decreased sensation
Patients with lepromatous leprosy, a more dissmeminated form of the disease have more of what type of immune response?
Th2 response (humoral immunity) in contrast to a Th1 response; therefore elevated levels of IL4, IL-5 and IL-10; affected tissues show extensive accumulation of acid-fast bacilli with in macrophages; develop more numerous, poorly demarcated plaques that are widespread across the body; over time, the bacterial load increases and the nodular lesions coalesce, causing the development of leonine facies and degeneration and loss of the nose and digits
A 64-year-old man has numerous .5 to 3 cm bullous skin lesions on his trunk and groin. He had itching for the past several weeks and developed the blisters a week ago. He has a history of hypertension and osteoarthritis. Biopsy shows separation of the dermis and epidermis. What is his likely condition?
What is the cause of bullous pemphigoid?
Antibodies against hemidesmosomes along the basement membrane of the dermal-epidermal junction
What finding would be expected in immunofluorescence of a biopsy of a blister from a patient with bullous pemphigoid?
IgG and/or C3 deposits in a linear pattern along the basement membrane
In a patient with Herpes Zoster what is the most likely finding on light microscompy of a biopsy from a vesicle base?
Intranuclear inclusions in keratinocytes and multinucleated giant cells (positive Tzanck smear)
Skin biopsy in a patient with Herpes Zoster would most likely show what finding?
Acantholysis (loss of intercellular connections) of keratinocytes and intraepidermal vesicles; dermal inflammatory infiltration and leukocytoclastic vasculitis may be present
A 36-year-old man has a 2-month history of pruritic skin rash over the elbows and knee. He has a prolonged history of episodic abdominal discomfort, flatulence and voluminous grease stools. Cardiopulmonary examination is normal. Abdomen is soft and nontender. Skin exam shows a papulovesicular skin rash in groups with erosion and excoriations. What condition does he likely have?
Dermatitis herpetiformis; characterized by erythematous pruritic papules, vesicles, and bullae that appear bilaterally and symmetrically on the extensor surfaces (eg. elbows, knees), upper back and buttocks; term "herpetiformis" refers to the resemblance of the clustered vesicular lesions to those seen in herpes simplex virus infections.
How is dermatitis herpetiformis characterized histologically?
Microabscesses containing fibrin and neutrophils at the dermal papillae tips; overlying basal cells become vacuolated and coalescing blisters form at the tips of the involved papillae
Describe the pathogenesis of dermatitis herpetiformis.
IgA antibodies against gliadin (a protein unique to gluten portion of wheat) or a gliadin/tissue transglutinase complex in the intestine; these antibodies appear to cause clinical disease by cross-reacting with epidermal transglutaminase
What disease is dermatitis herpatiformis strongly associated with?
How is celiac disease characterized histologically?
Increased intraepithelial lymphocytes, a variable loss of villus height and crypt hyperplasia
A 65-year-old male has several warty brown plaques on his back that appear as though they could be easily peeled off. What is the most likely diagnosis?
Seborrheic keratosis; benign epidermal tumor; common on middle-aged or elderly individuals; range from a few mm to several cm; "stuck on" appearance
What is the single most important measure to reduce the risk of transmission of hospital-acquired infections?
A 28-year-old has excessive scarring on her left shoulder after suffering a laceration to her shoulder during a motor vehicle. What is the cause of her excessive scarring?
Excessive collagen formation; results in keloids and hypertrophic scars; keloids usually extended beyond the borders of the original wound, do not regress, and recur after resection; unlike keloids, hypertrophic scars are limited to the area of the wound and may regress spontaneously (though that is uncommon); fibers lie in a parallel arrangement in hypertrophic scars and a disorganized fashion in keloids
Benign acanthosis nigricans is associated with what condition?
Insulin resistance; increased level of insulin and insulin-like growth factors stimulate epidermal and dermal proliferation
Malignant acanthosis nigricans is associated with what conditions?
Neoplasms, especially of the GI and GU tract; gastric adenocarcinoma is the most common cause of malignant acanthosis nigricans
A 17-year-old man has a painful subcutaneous nodule on his left forearm. Two weeks earlier he suffered a laceration to his forearm while playing soccer and had sutures placed. A biopsy of the lesion shows a granuloma. What is the most likely responsible for this patient's condition?
Reaction to a foreign body; can elicit a granulomatous response, seen clinically as a tender erythematous brown or purple papule, nodule, or plaque
How is urticaria characterized histologically?
Superficial dermal edema and lymphatic channel dilation with no epidermal changes; urticaria = "hives"
What is the pathogenesis of urticaria?
Focal mast cells degeneration (can be through antigen-induced degranulation of focal mast cells though IgE antibody sensitization or IgE-independent via substances that directly stimulate mast cell degranulation (eg. opiates, antibiotics, radiographic contrast media)) → microvascular hyperpermeability → formation of wheals that typically surface and resolve within hours (some episodes persist for days to months)
Name a potential complication of psoriasis.
Psoriatic arthritis: a deforming joint disease as seen with rheumatoid arthritis
A 58-year old has papules with overlying whitish scale that have a sandpaper-like texture on palpation. What are these lesions most likely?
Actinic keratoses; premalignant condition that can progress to squamous cell carcinoma
BRAF V600E mutation is associated with what condition?
Melanoma; seen in 40-60% of cases
What is BRAF?
A protein kinase involved in activation of signaling pathways for melanocyte proliferation
A 56-year-old male has a 1.6 cm mass in the right temporal lobe on MRI of his brain. A biopsy of the mass shows neoplasic tissue containing a mutation in the gene that encodes BRAF, a protein kinase. The point mutation results in a substitution of glutamic acid for valine at position 600 of the protein. What is the most likely diagnosis?
Melanoma; main risk factor for cutaneous melanoma is increased exposure to UV radiation
A 56-year-old male has an excisional biopsy of a pigmented lision on his right arm that is consistent with malignant melanoma. What is the most important prognostic indicator?
Depth of invasion
A 28-year-old has a biopsy of a pigmented skin lesion on her leg. The biopsy reveals nests of uniform round cells with inconspicuous nucleoli and few mitotic figures at the basal portion of the epidermis and upper dermis. What is the most likely diagnosis?
Compound melanocytic nevus; benign neoplasms composed of round uniform melanoctyes (nevus cells) that are mitotically quiescent; they are typically <6 mm in diameter and have a regular outline with a symmetrical, sharply demarcated boarder and a homogenous surface
How do melanocytic nevi progress?
Junctional nevi → compound nevi → intradermal nevi; Junctional nevi: aggregates of nevus cells along the dermoepidermal junction; typically appear as flat, black- to brown-pigmented macules with darker coloration in the center than the periphery and preserved skin markings; Intradermal nevi: older lesion in which the epidermal nests of nevus cells have been lost; remaining dermal nevus cells lose tyrosinase activity and produce little to no pigment; skin-to tan-colored, dome-shaped, and sometimes pedunculated