Skin pathology

Question 1

Atopic dermatitis

Answer 1

• Pruritic, erythematous, oozing rash with vesicles and edema
• Often involves face and flexor surfaces
• Type I HSR, associated wit asthma and allergic rhinitis

Question 2

Contact dermatitis

Answer 2

• Pruritic, erythematous, oozing rash with vesicles and edema
• Arises upon exposure to allergens
• Irritants: poison ivy and nickel jewelry (type IV HSR), irritant chemicals (e.g., detergents), drugs (e.g., PCN)
• Treatment: removal of offending agent, topical steroids, if needed

Question 3

Acne vulgaris

Answer 3

• Comedones (whiteheads and blackheads)
• Pustules (pimples)
• Nodules
• Due to chronic inflammation of hair follicles and sebaceous glands
• Hormone-related increase in sebum and excess keratin block follicles (comedones)
• Propionibacterium acnes infection leads to inflammation (pustules or nodules)
• Treatment: benzoyl peroxide

Question 4

Psoriasis

Answer 4

• Well-circumscribed salmon-colored plaques with silvery scale. Ausspitz sign
• Usually on extensor surfaces of elbows and knees, as well as the scalp and sacral area
• Due to excessive keratinocyte proliferation
• Possible autoimmune etiology
• Associated wit HLA-C allele on PSORS1 on chromosome 6
• 30% - facility history, HLA B13, 17
• Lesions often arises in areas of trauma (environmental trigger)
• Treatment: corticosteroids, UVA-light with psoralen, immune-modulating therapy

Question 5

Varicella (chickenpox)

Answer 5

• Viral infection of childhood
• Characterized by fever and a generalized vesicular eruption
• The varicella-zoster virus may remain latent for years in dorsal root ganglia

Question 6

Pemphigus vulgaris

Answer 6

• Autoimmune destruction of desmosomes
• Formation of severe intraepidermal bullae is characteristic
• First lesions often occur in the oral mucosa, and extensive skin involvement follows
• Due to IgG antibody against desmoglein
• IF highlights IgG surrounding keratinocytes (‘fish net’)
• Rupture easily - leaving large denuded surfaces subject to secondary infection

Question 7

Lichen planus

Answer 7

• Pruritic, planar, polygonal, purple papules
• Often with reticular white lines on surface (Wickham striae)
• Commonly involves wrists, elbows, and oral mucosa
• Inflammatory infiltrate composed of lymphocytes at the dermal-epidermal junction (‘saw-tooth’ appearance)
• Presence of apoptotic keratinocytes mainly in basal cell layer
• Etiology is unknown - associated with chronic hepatitis C virus infection and vaccination against hepatitis

Question 8

Bullous pemphigoid

Answer 8

• Resembles pemphigus vulgaris, but is much less severe
• Autoimmune destruction of hemidesmosome
• IgG autoantibodies agianst epidermal BM
• Presents as subepidermal blisters of skin filled with fluid containing eosinophils (between dermis and epidermis); oral mucosa is spared
• Tense bullae do not rupture easily

Question 9

Dermatitis herpetiformis

Answer 9

• Due to autoimmune deposition of IgA at tips of dermal papillae
• Presents as pruritic vesicles and bullae that are grouped
• Usually involves the extensor surfaces of the knees and elbows, scalp, upper back, and sacral area
• Dermal microabscesses with neutrophils and eosinophils at the tips of dermal papillae
• Associated with celiac disease
• Resolve with a gluten-free diet

Question 10

Erythema multiforme

Answer 10

• Presents with multiple type of lesions, including macules, papules, and vesicles
• Characteristically associated with a ‘target’ lesion resembling an archer’s bull’s eye
• Most commonly associated with HSV infection
• Usually hypersensitivity to coexistent infectious agents, various drugs, a concomitant connective tissue disorder, or an associated malignancy
• EM variants: Stevens-Johnson syndrome, Toxic epidermal necrolysis

Question 11

Vitiligo

Answer 11

• Localized loss of pigmentation
• Due to autoimmune destruction of melanocytes by toxic intermediates of melanin production or by neurochemical factors
• Associated with autoimmune disorders, such as Graves disease and Addison disease

Question 12

Albinism

Answer 12

• Congenital lack of pigmentation
  (1) Ocular albinism: melanin dysfunction limited to the eyes; X-linked disorder
  (2) Oculocutaneous albinism: involves eyes, skin, and hair; predisposes to actinic keratosis, basal and squamous cell carcinoma, and malignant melanoma; most often autosomal recessive
• Tyrosine-negative albinism - failure of conversion of tyrosine to DOPA
• Tyrosine-positive albinism - unknown etiology

Question 13

Freckle

Answer 13

• Increase of melanin pigment within basal keratinocytes - melanosomes
• Darkens when exposed to sunlight

Question 14

Lentigo

Answer 14

• Pigmented macule caused by melanocytic hyperplasia in the epidermis

Question 15

Melanocytic nevus

Answer 15

• Lesion classified as a benign tumor or hamartoma
• Nevus cells are derived from melanocytes and ordinarily occur in cluster or nests
  (1) Juntional nevus: confined to the epidermal-dermal junction, most common mole in children
  (2) Compound nevus: both at the epidermal-dermal junction and in the dermis
  (3) Intradermal nevus: cinfined to clusters within the dermis, most common mole in adults

Question 16

Blue nevus

Answer 16

• Pigmented nevi that are present at birth

- Characteristically include nodular foci of dendritic, highly pigmented melanocytes in the dermis

Question 17

Spitz nevus

Answer 17

• Most often occurs in children
• Generally benign, although an atypical variant with borderline behavior exists
• Often characterized by spindle-shaped cells and can be confused with malignant melanoma

Question 18

Dysplastic nevus

Answer 18

• Atypical, irregular pigmented lesion with disorderly proliferation of melanocytes, dermal fibrosis, and often subjacent dermal lymphocytic infiltration
• May transform into malignant melanoma
• Familial in some cases - autosomal dominant inheritance

Question 19

Lentigo maligna

Answer 19

• Nonfamilial precursor to lentigo maligna melanoma
• Irregular macular pigmented lesion on sun-exposed skin
• Characterized by atypical melanocytes at the epidermal-dermal junction

Question 20

Molluscum contagiosum

Answer 20

• Contagious viral disorder that occurs most often in children and adolescents
• Firm, pink, umbilicated, dome-shaped papules due to a DNA poxvirus
• Transmitted by direct contact

Question 21

Verruca vulgaris

Answer 21

• Common wart
• Benign papilloma caused by certain strain of HPV (3 and 10?) infection of keratinocytes
• Flesh-colored papules with rough surface
• Vacuolated cells (kilobytes) in the granular cell layer of the epidermis are characteristic
• Hands and feet are common locations

Question 22

Cellulitis

Answer 22

• Deeper (dermal) infection
• Usually due to S. aureus or S. pyogenes
• Presentss as a red, tender, swollen rash with fever
• Risk factors: recent surgery, trauma, insect bite
• Can progress to necrotizing fasciitis

Question 23

Staphylococcal scalded skin syndrome

Answer 23

• Sloughing of skin with erythematous rash and fever
• Leads to significant skin loss
• Due to S. aureus infection
• Exfoliative A and B toxins result in epidermolysis of stratum granulosum

Question 24

Actinic keratosis

Answer 24

• Premalignant epidermal lesion caused by chronic excessive exposure to sunlight
• Characterized by roughness, scaling, poorly demarcated plaques on the face, neck, upper trunk, or extremities

Question 25

Acanthosis nigricans

Answer 25

• Epidermal hyperplasia with darkening of skin (‘velvet-like’ skin)
• Sometimes a marker for visceral malignancy (stomach, lung, breast, uterus) and is often seen in the setting of diabetes and other endocrinopathies
• Characterized by acanthosis and hyperpigmentation

Question 26

Xanthoma

Answer 26

• Most often associated with hypercholesterolemia
• Characterized by yellowish papules or nodules composed of focal dermal collections of lipid-laden histiocytes
• Occurs most frequently on the eyelids

Question 27

Hemangioma

Answer 27

• Capillary hemangioma: small, blood-filled capillaries lined with a single layer of endothelium
  (1) Port-wine stain - purple-red area on the face or neck
  (2) Strawberry hemangioma - bright-red raised lesion
  (3) Chery hemangioma - small, domed-shaped red papule
• Cavernous hemangioma: large, endothelium-lined spaces in the dermis and subdermis

Question 28

Squamous cell carcinoma (skin)

Answer 28

• Common malignant skin tumor
• Most often locally invasive; fewer than 5% of tumors metastasize
• Associated most often with excessive exposure to sunlight
• Other risk factors: albinism, xeroderma pigmentosum, immunosuppressive therapy, arsenic poisoning, chronic inflammation
• Usually involves sun-exposed areas - face and back of hands, lower part of face - lower lip
• Presents as scaling, indurated, ulcerated nodule
• Invasion of dermis by sheets and islands of neoplastic epidermal cells, often with keratin “pearls”, is characteristic

Question 29

Basal cell carcinoma (skin)

Answer 29

• Most common of all malignant skin tumors
• Risk factors: exposure to sunlight (UVB), albinism, and xeroderma pigmentosum
• Presents as pearly papule, often with overlying telangiectatic vessels
• Characterized by clusters of darkly staining basaloid cells with a typical palisade arrangement of the nuclei of the cells at the periphery of the tumor cell clusters
• Tends to involve the upper part of face - upper lip
• Can be locally aggressive, ulcerate, and bleed
• Matastasis is rare

Question 30

Malignant melanoma

Answer 30

• Malignant neoplasm of melanocytes
• Most common cause of death from skin cancer
• Risk factors: exposure to sunlight, albinism, xeroderma pigmentosum
• Recognized as mole-like growth with ‘ABCD’: Asymmetry, Borders are irregular, Color is not uniform, Diameter>6mm
• Characterized by two growth phases:
• Radial growth horizontally along epidermis and superficial dermis
• Vertical growth into deep dermis (higher risk of metastasis)
• Four major subtypes of melanoma:
  (1) Lentigo maligna melanoma - radial growth
  (2) Superficial spreading melanoma - most common subtype, radial growth
  (3) Nodular melanoma - vertical growth, push the epidermis up; poorest prognosis of the subtypes
  (4) Acral-lentiginous melanoma - arises on palms or soles, often i dark-skinned persons. Not related to UV-light exposure

Question 31

Dermatomyositis

Answer 31

• Skin and muscle inflammatory disorder
• Skin rash - liliac discoloration of the upper eyelids with periorbital edema
• Grotton lesions - scaling red patches over the knuckles, elbows, knees
• Muscle weakness (proximal parts)
• Interstial lung disease, dysphagia, vasculitis, etc.
• 40% of adult patients have cancer