Chronic, inflammatory rash with increased and rapid epidermal proliferation resulting in accumulation of stratum corneum
Classic lesion: Well-circumscribed, erythematous plaque with a dry, silvery scale appearing on extensor surfaces of the limbs.
Lesions are bilateral and symmetrical in distribution.
Most commonly on extensor surfaces (knees, elbows, nails)
Presents as erythematous patches and plaques covered with white scales
Associated with "Auspitz" sign - Tugging gently on scale results in pinpoint bleeding
Associated with arthritis, classically sero-negative and exhibiting a predilection for the distal inter-phalangeal joints
Guttate Psoriasis
Guttate - Latin for "drop-like."
SImilar in color and texture but shaped like drops or smaller circular lesions than in the classic form
Pustular Psoriasis
Multiple, fresh, yellow pustules AND older, dry, brown macules on the palms and soles
Classically mis-diagnosed as vesicular tinea pedis.
Psoriatic Nail disease
"oil-drop" staining
pitting - small depressions on the surface of the nail plate
Sub-ungual debris and hyperkeratosis
Transverse grooves
Looks similar to onychomycosis and my coexist with onychomycosis
Bacterial Infections of the skin
Impetigo
A superficial skin infection due to S. Pyogenes & S. aureus, alone or together. Especially common in children in hot, humid climates
Small, thin-walled vesicles or pustules on an erythematous base rupture to form characteristic yellow-brown (honey-colored) crusts. Removal of the crusts reveal a superficial, moist base. Lesions do not ulcerate.
Commonly found on the face and extremities
Involved areas may be pruritic. Regional lymph node involvement is common but other systemic manifestations are rare.
A superficial skin infection caused by Group A Strep and S. Aureus
Begins as vesicles or bullae that rupture to form cursts. Removal of crust reveals an ulceration. Heals with scarring
Lesions are typically erythematous, circular, and multiple. Most commonly involve the lower extremities.
Treatment:
Oral antibiotics (Dicloxacillin)
Erysipelas and Cellulitis
When a Strep infection spreads into the dermal lymphatics, erysipelas occurs and when it involves the deeper dermis and subcutaneous fat, cellulitis occurs.
S. Pyogenes releases enzymes to facilitate rapid spread of the infection through tissue planes and prevent abscess formation. Edema, erythema, and heat develop. The enzymes also produce systemic manifestations (fever, tachycardia, confusion, and hypotension)
Predisposing factors: edema, tinea pedis, previous trauma to skin - burns, surgery, or radiation.
Most common sites are the face of lower extremities
Erysipelas unlike cellulitis has a sharply demarcated and elevated border.
Both needle aspiration and skin biopsy of the lesion usually fail to yield organisms
Causitive agents: Usually Strep
S. aureus - around abscess or open wound
H influenzae - facial cellulitis in young children (6-36 months)
P. Multocida - cat and dog bites
P. aeroginosa & other gram (-) organisms - common in immunocompromised hosts
Treatment: Mild - oral antibiotics
Severe - IV antibotics
Signs and symptoms may worsen after therapy is initiated because the antimicrobial rapidly kills the bacteria causing the release of potent enzymes.
Furuncles and Carbuncles
A furuncle is an infection of the hair follicle that produces an inflammatory nodule with a pustule center through which the hair emerges.
A Carbuncle affects several adjacent hair follicles and begins as a nodule which enlarges to create an inflammatory mass that discharges pus from multiple follicular orifices. They occur predominantly on the back of the neck and is more common in diabetics.
S. aureus is the most common cause of both.
Treatment:
Small furuncles - moist heat to promote drainage
Carbuncles and Large Furuncles - Incision and Drainage
Folliculitis
Inflammation at the opening of the hair follicle. Pathogenesis involves......