Musculoskeletal, Skin, and Connective Tissue - Pathology (2) Flashcards
1
Q
Scleroderma (systemic sclerosis)
- Definition
- Findings
- 2 major types:
- Diffuse scleroderma
- Limited scleroderma
A
- Definition
- Excessive fibrosis and collagen deposition throughout the body.
- Findings
- Commonly sclerosis of skin, manifesting as puffy and taut skin [A] [B] with absence of wrinkles.
- Also sclerosis of renal, pulmonary (most common cause of death), cardiovascular, and GI systems.
- 75% female.
- 2 major types:
-
Diffuse scleroderma
- Widespread skin involvement, rapid progression, early visceral involvement.
- Associated with anti-Scl-70 antibody (anti-DNA topoisomerase I antibody).
-
Limited scleroderma
- Limited skin involvement confined to fingers and face.
- Also with CREST involvement: Calcinosis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia.
- More benign clinical course.
- Associated with antiCentromere antibody (C for CREST).
-
Diffuse scleroderma

2
Q
Dermatologic macroscopic terms (morphology)
- For each
- Characteristics
- Examples
- Macule
- Patch
- Papule
- Plaque
- Vesicle
A
- Macule [A]
- C: Flat lesion with well-circumscribed change in skin color < 1 cm
- Ex: Freckle, labial macule
- Patch [B]
- C: Macule > 1 cm
- Ex: Large birthmark (congenital nevus)
- Papule [C]
- C: Elevated solid skin lesion < 1 cm
- Ex: Mole (nevus), acne
- Plaque [D]
- C: Papule > 1 cm
- Ex: Psoriasis
- Vesicle [E]
- C: Small fluid-containing blister < 1 cm
- Ex: Chickenpox (varicella), shingles (zoster)

3
Q
Dermatologic macroscopic terms (morphology)
- For each
- Characteristics
- Examples
- Bulla
- Pustule
- Wheal
- Scale
- Crust
A
- Bulla [F]
- C: Large fluid-containing blister > 1 cm
- Ex: Bullous pemphigoid
- Pustule [G]
- C: Vesicle containing pus
- Ex: Pustular psoriasis
- Wheal [H]
- C: Transient smooth papule or plaque
- Ex: Hives (urticaria)
- Scale [I]
- C: Flaking off of stratum corneum
- Ex: Eczema, psoriasis, SCC
- Crust [J]
- C: Dry exudate
- Ex: Impetigo

4
Q
Dermatologic microscopic terms
- For each
- Characteristics
- Examples
- Hyperkeratosis
- Parakeratosis
- Spongiosis
- Acantholysis
- Acanthosis
A
- Hyperkeratosis
- C: Increased thickness of stratum corneum
- Ex: Psoriasis, calluses
- Parakeratosis
- C: Hyperkeratosis with retention of nuclei in stratum corneum
- Ex: Psoriasis
- Spongiosis
- C: Epidermal accumulation of edematous fluid in intercellular spaces
- Ex: Eczematous dermatitis
- Acantholysis
- C: Separation of epidermal cells
- Ex: Pemphigus vulgaris
- Acanthosis
- C: Epidermal hyperplasia (increased spinosum)
- Ex: Acanthosis nigricans
5
Q
Pigmented skin disorders
- Albinism
- Melasma (chloasma)
- Vitiligo
A
- Albinism
- Normal melanocyte number with decreased melanin production [A] due to decreased tyrosinase activity or defective tyrosine transport.
- Can also be caused by failure of neural crest cell migration during development.
- Increased risk of skin cancer.
- Melasma (chloasma)
- Hyperpigmentation associated with pregnancy (“mask of pregnancy” [B]) or OCP use.
- Vitiligo
- Irregular areas of complete depigmentation [C].
- Caused by autoimmune destruction of melanocytes.

6
Q
Common skin disorders
- Verrucae
- Melanocytic nevus
- Urticaria
A
- Verrucae
- Warts
- Caused by HPV.
- Soft, tan-colored, cauliflower-like papules [A].
- Epidermal hyperplasia, hyperkeratosis, koilocytosis.
- Condyloma acuminatum on genitals [B].
- Melanocytic nevus
- Common mole.
- Benign, but melanoma can arise in congenital or atypical moles.
- Intradermal nevi are papular [C].
- Junctional nevi are flat macules [D].
- Urticaria
- Hives.
- Pruritic wheals that form after mast cell degranulation [E].
- Characterized by superficial dermal edema and lymphatic channel dilation.

7
Q
Common skin disorders
- Ephelis
- Atopic dermatitis (eczema)
- Allergic contact dermatitis
A
- Ephelis
- Freckle.
- Normal number of melanocytes, increased melanin pigment [F].
- Atopic dermatitis (eczema)
- Pruritic eruption, commonly on skin flexures.
- Often associated with other atopic diseases (asthma, allergic rhinitis).
- Usually starts on the face in infancy [G] and often appears in the antecubital fossae [H] thereafter.
- Allergic contact dermatitis
- Type IV hypersensitivity reaction that follows exposure to allergen.
- Lesions occur at site of contact (e.g., nickel [I], poison ivy, neomycin [J]).

8
Q
Common skin disorders
- Psoriasis
- Seborrheic keratosis
A
- Psoriasis
- Papules and plaques with silvery scaling [K], especially on knees and elbows.
- Acanthosis with parakeratotic scaling (nuclei still in stratum corneum).
- Increased stratum spinosum, decreased stratum granulosum.
- Auspitz sign (arrow in [L])—pinpoint bleeding spots from exposure of dermal papillae when scales are scraped off.
- Can be associated with nail pitting and psoriatic arthritis.
- Seborrheic keratosis
- Flat, greasy, pigmented squamous epithelial proliferation with keratin-filled cysts (horn cysts) [M].
- Looks “stuck on” [N] [O].
- Lesions occur on head, trunk, and extremities.
- Common benign neoplasm of older persons.
- Leser-Trélat sign—sudden appearance of multiple seborrheic keratoses, indicating an underlying malignancy (e.g., GI, lymphoid).

9
Q
Infectious skin disorders
- Impetigo
- Cellulitis
- Necrotizing fasciitis
A
- Impetigo
- Very superficial skin infection.
- Usually from S. aureus or S. pyogenes.
- Highly contagious.
- Honey-colored crusting [A].
- Bullous impetigo [B] has bullae and is usually caused by S. aureus.
- Cellulitis
- Acute, painful, spreading infection of dermis and subcutaneous tissues.
- Usually from S. pyogenes or S. aureus.
- Often starts with a break in skin from trauma or another infection [C].
- Necrotizing fasciitis
- Deeper tissue injury, usually from anaerobic bacteria or S. pyogenes.
- Results in crepitus from methane and CO2 production.
- “Flesh-eating bacteria.”
- Causes bullae and a purple color to the skin [D].

10
Q
Infectious skin disorders
- Staphylococcal scalded skin syndrome
- Hairy leukoplakia
A
- Staphylococcal scalded skin syndrome
- Exotoxin destroys keratinocyte attachments in the stratum granulosum only (vs. toxic epidermal necrolysis, which destroys the epidermal-dermal junction).
- Characterized by fever and generalized erythematous rash with sloughing of the upper layers of the epidermis that heals completely.
- Seen in newborns and children [E].
- Hairy leukoplakia
- White, painless plaques on the tongue that cannot be scraped off [F].
- EBV mediated.
- Occurs in HIV‑positive patients.

11
Q
Pemphigus vulgaris
- Type of disorder
- Definition
- Findings
A
- Type of disorder
- Blistering skin disorder
- Definition
- Potentially fatal autoimmune skin disorder with IgG antibody against desmoglein (component of desmosomes).
- Findings
- Flaccid intraepidermal bullae [A] caused by acantholysis (keratinocytes in stratum spinosum are connected by desmosomes)
- Oral mucosa also involved.
- Immunofluorescence reveals antibodies around epidermal cells in a reticular (net-like) pattern [B].
- Nikolsky sign (+) (separation of epidermis upon manual stroking of skin).
- Flaccid intraepidermal bullae [A] caused by acantholysis (keratinocytes in stratum spinosum are connected by desmosomes)

12
Q
Bullous pemphigoid
- Type of disorder
- Definition
- Findings
A
- Type of disorder
- Blistering skin disorder
- Definition
- Less severe than pemphigus vulgaris.
- Involves IgG antibody against hemidesmosomes
- Epidermal basement membrane
- Antibodies are “bullow” the epidermis.
- Findings
- Tense blisters [C] containing eosinophils affect skin but spare oral mucosa.
- Immunofluorescence reveals linear pattern at epidermal-dermal junction [D].
- Nikolsky sign (-).

13
Q
Dermatitis herpetiformis
- Type of disorder
- Findings
A
- Type of disorder
- Blistering skin disorder
- Findings
- Associated with celiac disease.
- Pruritic papules, vesicles, and bullae (often found on elbows) [E].
- Deposits of IgA at the tips of dermal papillae.

14
Q
Erythema multiforme
- Type of disorder
- Associations
- Presentation
A
- Type of disorder
- Blistering skin disorder
- Associated with…
- Infections (e.g., Mycoplasma pneumoniae, HSV)
- Drugs (e.g., sulfa drugs, β-lactams, phenytoin)
- Cancers
- Autoimmune disease.
- Presents with multiple types of lesions
- Macules, papules, vesicles, and target lesions (look like targets with multiple rings and a dusky center showing epithelial disruption) [F].

15
Q
Stevens-Johnson syndrome
- Type of disorder
- Definition
- Findings
A
- Type of disorder
- Blistering skin disorder
- Definition
- A more severe form of Stevens-Johnson syndrome with > 30% of the body surface area involved is toxic epidermal necrolysis [H] [I].
- Usually associated with adverse drug reaction.
- Findings
- Characterized by fever, bulla formation and necrosis, sloughing of skin, and a high mortality rate.
- Typically 2 mucous membranes are involved [G], and skin lesions may appear like targets as seen in erythema multiforme.

16
Q
Acanthosis nigricans
- Definition
- Associations
A
- Definition
- Epidermal hyperplasia causing symmetrical, hyperpigmented, velvety thickening of skin, especially on neck or in axilla [A].
- Associated with…
- Hyperinsulinemia (e.g., diabetes, obesity, Cushing syndrome)
- Visceral malignancy (e.g., gastric adenocarcinoma).

17
Q
Actinic keratosis
- Definition
- Findings
A
- Definition
- Premalignant lesions caused by sun exposure.
- Risk of squamous cell carcinoma is proportional to degree of epithelial dysplasia.
- Findings
- Small, rough, erythematous or brownish papules or plaques [B].

18
Q
Erythema nodosum
- Definition
- Associations
A
- Definition
- Painful inflammatory lesions of subcutaneous fat, usually on anterior shins.
- Associations
- Often idiopathic, but can be associated with sarcoidosis, coccidioidomycosis, histoplasmosis, TB, streptococcal infections, leprosy, and Crohn disease [C].

19
Q
Lichen Planus
- Definition
- Findings
A
- Definition
- Sawtooth infiltrate of lymphocytes at dermal-epidermal junction.
- Associated with hepatitis C.
- Findings
- 6 P’s of lichen Planus: Pruritic, Purple, Polygonal Planar Papules and Plaques [D]
- Mucosal involvement manifests as Wickham striae (reticular white lines).

20
Q
Pityriasis rosea
A
- “Herald patch” followed days later by “Christmas tree” distribution [E].
- Multiple plaques with collarette scale.
- Self-resolving in 6–8 weeks.

21
Q
Sunburn
- Definition
- Findings
- UVA vs. UVB
A
- Definition
- Acute cutaneous inflammatory reaction due to excessive UV irradiation.
- Findings
- Causes DNA mutations, inducing apoptosis of keratinocytes.
- Can lead to impetigo [F] and skin cancers (basal cell carcinoma, squamous cell carcinoma, and melanoma).
- UVA vs. UVB
- UVA is dominant in tanning and photoaging
- UVB is dominant in sunburn.

22
Q
Basal cell carcinoma (438)
- Definition
- Findings
A
- Definition
- Most common skin cancer.
- Found in sun-exposed areas of body.
- Locally invasive, but almost never metastasizes.
- Findings
- Pink, pearly nodules, commonly with telangiectasias, rolled borders, and central crusting or ulceration [A].
- BCCs also appear as nonhealing ulcers with infiltrating growth [B] or as a scaling plaque (superficial BCC) [C].
- Basal cell tumors have “palisading” nuclei [D].

23
Q
Squamous cell carcinoma (438)
- Definition
- Findings
- Actinic keratosis
- Keratoacanthoma
A
- Definition
- Second most common skin cancer.
- Associated with excessive exposure to sunlight, immunosuppression, and occasionally arsenic exposure.
- Locally invasive, but may spread to lymph nodes and will rarely metastasize.
- Associated with chronic draining sinuses.
- Findings
- Commonly appears on face [E], lower lip [F], ears, and hands.
- Ulcerative red lesions with frequent scale.
- Histopathology: keratin “pearls” [G].
-
Actinic keratosis
- A scaly plaque
- A precursor to squamous cell carcinoma.
-
Keratoacanthoma
- A variant that grows rapidly (4–6 weeks)
- May regress spontaneously over months [H].

24
Q
Melanoma (438)
- Definition
- Findings
- Treatment
A
- Definition
- Common tumor with significant risk of metastasis.
- S-100 tumor marker.
- Depth of tumor correlates with risk of metastasis.
- Associated with sunlight exposure; fair-skinned persons are at increased risk.
- At least 4 different types of melanoma [I] [J] [K] [L].
- Often driven by activating mutation in BRAF kinase.
- Findings
- Look for the ABCDEs: Asymmetry, Border irregularity, Color variation, Diameter > 6 mm, and Evolution over time.
- Treatment
- Primary treatment is excision with appropriately wide margins.
- Metastatic or unresectable melanoma in patients with BRAF V600E mutation may benefit from vemurafenib, a BRAF kinase inhibitor.
