The Skin 279

20 A 30-year-old woman with chronic hepatitis B presents with numerous red skin lesions that she has had for 5 days. Physical examination reveals multiple, purpuric, 2- to 4-mm papules on the skin (shown in the image). The pap-ules did not blanch under pressure. Biopsy of lesional skin shows necrotizing leukocytoclastic venulitis. Immunofl uo-rescence studies disclose immune complex deposition in vascular walls. Which of the following is the most likely diagnosis?

(A) Allergic contact dermatitis(B) Dermatitis herpetiformis(C) Erythema multiforme(D) Erythema nodosum(E) Hypersensitivity angiitis

21 A 20-year-old man presents to his family physician for treat-ment of itching after exposure to poison ivy. The patients hands and arms appeared red and were covered with oozing blisters and crusts (shown in the image). Which of the follow-ing represents the most important step in the pathogenesis of the sensitization phase of injury in this patient?

(A) Development of spongiosis(B) Infi ltration of the epidermis by neutrophils(C) Migration of Langerhans cells into dermal lymphatics(D) Rapid increase in vascular permeability(E) Separation of the epidermis from the dermis mediated by

eosinophils

17 A 14-year-old boy presents with a 6-month history of erythematous papules on his face. Physical examination reveals numerous blackheads over the forehead and cheeks. Which of the following bacteria is associated with the devel-opment of these lesions?(A) Clostridium sp.(B) Lactobacillus sp.(C) Propionibacterium sp.(D) Staphylococcus sp.(E) Streptococcus sp.

18 A 30-year-old man presents with fl at-topped papules that have appeared gradually on the fl exor surfaces of his wrists. White streaks and patches are also found on the buccal mucosa of the patients mouth. Histologically, the lesions showed hyper-keratosis, thickening of the stratum granulosum, and a band-like infi ltrate of lymphocytes and macrophages in the upper dermis, disrupting the basal layer of the epidermis. Lympho-cytes were mostly of the CD4+ immunophenotype. Which of the following is the appropriate diagnosis?(A) Dermatitis herpetiformis(B) Erythema multiforme(C) Erythema nodosum(D) Hypersensitivity angiitis(E) Lichen planus

19 A 66-year-old woman presents with a 5-year history of ery-thematous, scaly patches on her buttocks. Physical exami-nation reveals plaques with telangiectases, atrophy, and pigmentation. Biopsy of lesional skin shows that the epidermis and papillary dermis are expanded by an extensive infi ltrate of atypical lymphocytes. These infi ltrating lymphocytes most likely express which of the following cluster of differentia-tion cell surface markers?

(A) CD4(B) CD9(C) CD15(D) CD20(E) CD31

The Skin 281

12 The answer is E: Human papillomavirus. Verruca vulgaris, also known as the common wart, is an elevated papule with a verrucous (papillomatous) surface. The warts may be single or multiple and are most frequent on the dorsal surfaces of the hands or on the face. Several human papillomavirus types, including types 2 and 4, have been demonstrated in verruca vulgaris. No malignant potential is recognized. The other choices do not induce papillomas.Diagnosis: Verruca vulgaris

13 The answer is D: Erythema nodosum (EN). EN is a cutaneous disorder that manifests as self-limited, nonsuppurative, tender nodules over the extensor surfaces of the lower extremities. It is triggered by exposure to a variety of agents, including drugs and microorganisms (bacteria, viruses, and fungi), and occurs in association with a number of benign and malignant systemic diseases. The early neutrophilic infl ammation sug-gests that EN may be a response to the activation of comple-ment, with resulting neutrophilic chemotaxis. The subsequent appearance of chronic infl ammation, foreign body giant cells, and fi brosis is secondary to necrosis of adipose tissue. The other choices do not feature this distinctive histology.Diagnosis: Erythema nodosum

14 The answer is B: Bullous pemphigoid (BP). BP is a common, autoimmune, blistering disease with clinical similarities to pemphigus vulgaris (thus, the term pemphigoid) but in which acantholysis is absent. Complement-fi xing IgG antibodies are directed against two basement membrane proteins, BPAG1 and BPAG2. In contrast to pemphigus vulgaris (choice E), immu-nofl uorescent studies demonstrate linear deposition of C3 and IgG along the epidermal basement membrane zone. The other choices do not feature antibasement membrane antibodies.Diagnosis: Bullous pemphigoid

15 The answer is B: IgA deposits in dermal papillae. Derma-titis herpetiformis is an intensely pruritic cutaneous erup-tion related to gluten sensitivity, which is characterized by urticaria-like plaques and vesicles over the extensor surfaces of the body. Genetically predisposed patients may develop IgA antibodies to components of gluten in the intestines. The resulting IgA complexes then gain access to the circulation and are deposited in the skin. The release of lysosomal enzymes by infl ammatory cells cleaves the epidermis from the dermis. The other choices are not typical histologic fi ndings in dermatitis herpetiformis.Diagnosis: Dermatitis herpetiformis

16 The answer is C: Granular distribution of immune complexes in the basement membrane zone. The patient exhibits signs and symptoms of systemic lupus erythematosus (SLE), a disorder characterized by a variety of autoantibodies and other immune abnormalities indicating B-cell hyperactivity. Epidermal cellu-lar damage initiated by light or other exogenous agents causes the release of a large number of antigens, some of which may return to the skin in the form of immune complexes. Immune complexes are also formed in the skin by a reaction of local DNA with antibody that may also be deposited beneath the epidermal basement membrane zone. The other choices are not features of SLE.Diagnosis: Systemic lupus erythematosus

of the epidermis are thickened several-fold in the rete pegs and are frequently thinner over the dermal papillae. The capillaries of the papillae are dilated and tortuous. Neutrophils emerge at their tips and migrate into the epidermis above the apices of the papillae. Neutrophils may become localized in the epi-dermal spinous layer or in small Munro microabscesses in the stratum corneum. The dermis below the papillae exhibits a varying number of mononuclear infl ammatory cells (choices A and E) around the superfi cial vascular plexuses.Diagnosis: Psoriasis

9 The answer is C: Epidermolysis bullosa (EB). EB comprises a heterogeneous group of disorders loosely bound by their hereditary nature and by a tendency to form blisters at sites of minor trauma. EB simplex has been attributed to mutations of genes encoding cytokeratin intermediate fi laments. The clini-cal spectrum of the disease ranges from a minor annoyance to a widespread, life-threatening blistering disease. These blis-ters are almost always noted at birth or shortly thereafter. The classifi cation of these disorders is based on the site of blister for-mation in the basement membrane zone. Although epidermo-lytic EB is cosmetically disturbing and sometimes debilitating, it is not life threatening. Blisters seen in bullous pemphigoid (choice A) and pemphigus vulgaris (choice E) are associated with immunoglobulin deposits that are visualized by direct immunofl uorescence microscopy. Dermatitis herpetiformis (choice B) occurs at a later age and is associated with gluten hypersensitivity. In ichthyosis vulgaris (choice D), scaly skin results from increased cohesiveness of the stratum corneum.Diagnosis: Epidermolysis bullosa

10 The answer is B: Desmoglein-3. Pemphigus vulgaris is an autoimmune disease caused by autoantibodies to a keratino-cyte antigen. The characteristic lesion is a large, easily ruptured blister that leaves extensive denuded or crusted areas. Supra-basal dyshesion results in a blister that has an intact basal layer as a fl oor and the remaining epidermis as a roof. The blister contains a moderate number of lymphocytes, macrophages, eosinophils, and neutrophils. Distinctive, rounded keratin-ocytes (termed acantholytic cells) are shed into the vesicle during the process of dyshesion. Circulating IgG antibodies in patients with pemphigus vulgaris react with an epidermal surface antigen called desmoglein-3, a desmosomal protein. Antigenantibody union results in dyshesion, which is aug-mented by the release of plasminogen activator and, hence, the activation of plasmin. This proteolytic enzyme acts on the intercellular substance and may be the dominant factor in dys-hesion. None of the other choices are related to the pathogen-esis of pemphigus vulgaris.Diagnosis: Pemphigus vulgaris

11 The answer is A: Basal cell carcinoma (BCC). BCC is the most common malignant tumor in persons with pale skin. Although it may be locally aggressive, metastases are exceed-ingly rare. BCC usually develops on the sun-damaged skin of people with fair skin and freckles. The tumor is composed of nests of deeply basophilic epithelial cells with narrow rims of cytoplasm that are attached to the epidermis and protrude into the subjacent papillary dermis. Basaloid keratinocytes are rarely seen in squamous cell carcinoma (choice D) and are not encountered in the other choices.Diagnosis: Basal cell carcinoma