Papulosquamous Disorders Flashcards
What is a papulosquamous disorder? Also, give the four most common non-infectious ones.
Dry rashes - well defined plaques with scale
- Psoriasis
- Seborrheic dermatitis
- Pityriasis rosea
- Lichen planus
What factors affect your probability of developing psoriasis?
Genetics - psoriasis is highly genetically linked. 1/3 have a relative with the disease.
Environmental factors - influence the penetrance of psoriasis and frequency of exacerbations
Immune system - modulate the severity of the exacerbations
What is the frequency of psoriatic arthritis and what is its clinic presentation/?
Affects up to 30% of psoriasis patients, usually 10 years after first appearance of symptoms
Presents as asymmetric or symmetric arthritis, affecting any joint, but usually fingers and toes are most affected.
What is the pathogenesis of psoriasis?
Overproduction of Th1 cytokines leads to immune-mediated proliferation of basal cell keratinocytes -> hyperproliferation and rapid turnover
May be sometimes associated with recent strep infection
What are classical findings on skin biopsy of psoriasis?
- Acanthosis - epidermal hyperplasia
- Parakeratosis - hyperkeratosis with renteion of keratinocyte nuclei in stratum corneum
- Neutrophils in stratum corneum
- Thinning of epidermis above elongated dermal papillae
What are neutrophils in the stratum corneum called in the context of psoriasis?
Monro microabscesses
What clinical sign occurs as a result of thinning of the epidermis above elongated dermal papillae in psoriasis?
Auspitz sign - easy bleeding (microhemorrhage) when the scaling is picked off since the dermis is so superficial
Where do psoriasis plaques classically appear, and what do they look like?
Papules and plaques with silvery scaling, classically appear on flexor surfaces (knees and elbows).
Around the umbilicus is also another relatively pathognomonic spot
How can RA and psoriatic arthritis be differentiated?
RA - affects MCP and PIP joints
PA - affects DIP joints
-> can progress to arthritis mutilans
What can local plaques as well as guttate form resemble in psoriasis? (ddx)
Local plaques - eczema or seborrheic dermatitis
Guttate formm - secondary syphilis or pityriasis rosea
What is the Koebner phenomenon? Does this occur in psorasis?
When skin lesions appear at the site of physical trauma, i.e. scratching, sunburn, surgery
Yes, this occurs in psoriasis very prominently
Other the Koebnerization (trauma), what are some other classical triggers of psorasis?
Infections
stress
Medications i.e. beta-blockers, ACE inhibitors, lithium
Other environmental causes
What nail changes are common of psorasis?
- Pitting (depressions in nails)
- Oil drop / salmon patch - yellow-red discoloration looking like drop of oil in nail bed
- Subungual hyperkeratosis may lead to onycholysis (nail separates from underlying attachment, as in onychomycosis)
What is guttate psoriasis and who tends to get it? When does it develop?
Psoriasis characterized by small, thin pink papules and plaques with scale in a pityriasis rosea distribution (Trunk, abdomen, and upper thighs).
It is the most common subtype in children and young adults, develops after Group A beta-hemolytic strept pharyngeal / perianal infection
What is inverse type psoriasis?
Scale forms but tends to be on skin fold areas (intertriginous), especially inframammary, between trunk folds, and between the but cheeks
What is pustular type psoriasis?
Generalized or acute, can be limited to palms and soles
-> monomorphic sterile pustules
What are the general treatments for psoriasis?
- Topical corticosteroids
- Phototherapy, especially psoralen + UVA therapy to immunosuppress = PUVA
- Immunomodulating therapy -> methotrexate, TNF inhibitors, etc
What is seborrheic dermatitis and where does it tend to occur in adults?
A chronic inflammatory disease which occurs in areas with high sebaceous gland activity: scalp, eyebrows, eyelashes, nasolabial folds, posterior auricular fold, and chest
What is a typical infantile distribution of seborrheic dermatitis?
“Cradle cap” - greasy adherent scale over the vertex of the scalp
Diaper area and trunk are also commonly involved
What does seborrheic dermatitis look like morphologically and what is it called when on the scalp?
Erythematous scaling, which accumulates and becomes thick over scalp. Can cause inflammation and hair loss.
- > looks like mild psoriasis
- > scaling which peels off is called “dandruff”.
What condition is highly associated with seborrheic dermatitis?
AIDS -> typically occurs before onset of AIDS symptoms.
The condition itself is thought to be related to Malassezia ovalis.
What is the differential diagnosis for an erythematous rash in the diaper area of an infant?
- Seborrheic dermatitis
- Diaper dermatitis (irritant contact dermatitis due to feces, urine, or baby powder, with macerated skin)
- Candida
- Psoriasis
What are the treatments for seborrheic dermatitis?
Frequent washing of all affected areas (wash out the sebaceous glands) as well as an antiseborrheic shampoo (i.e. pyrithione zinc)
Topic antifungals may help (remember Malassezia ovalis), and also topical steroids.
What typically precedes the development of a generalized rash in pityriasis rosea?
- URI - in as many as 70% of patients
2. Herald patch - 2-10 cm large, erythematous patch typically on abdomen or proximal extremities, but may be hidden
What happens in pityriasis rosea after the herald patch appears?
7-14 days later -> small patches of erythematous, flaky, oval-shaped rash appear on torso (appear like guttate psoriasis). They can be hyperpigmented in blacks.
Where do all of the lesions spread to in pityriasis rosea?
Lesions often spread on torso / follow ribline in a “Christmas tree” distribution (following lines of blaschkow / cleavage in their ovoid long axis).
Might reach proximal extremities, but typically do NOT appear on the face.
Think Rudolph the red ROSE reindeer to remember the association between rosea and christmas tree distribution
What type of scaling do lesions of pityriasis rosea show?
Collarette scale - Lesion is attached at the periphery and more loose at the center, appears as a ring of scale.
How do you tell pityriasis rosea from secondary syphilis quite easily, and what is the prognosis of the disease?
Secondary syphilis will show a rash on palms and soles. Pityriasis rosea typically does not involve the hands and face.
Prognosis of PR -> resolves spontaneously in 6-8 weeks.
Who tends to get pityriasis rosea and is it contagious?
Typically patients 10-35 years old, thought to be related to HHV-6, occurs in small epidemics in fraternity houses / military bases, but is thought NOT to be contagious somehow
What are the 5 P’s of Lichen Planus?
Pruritic, planar (flat-topped), polygonal, purple, papules
What will close inspection of the surface of Lichen Planus show?
Wickham’s striae - Lacy, reticular pattern of crisscrossed, whitish lines
Where do Lichen Planus lesions occur?
Flexor surfaces of wrists and forearms (elbows), ankles, lumbar back
Can involve mucuous membranes, especially buccal mucosa of mouth, and even genitals (appears as ulcers).
What is one characteristic feature of the pruritis in Lichen Planus?
Patient will say the itching is very severe, but there will be minimal excoriation of the lesions since they are very tender
What is thought to be the cause of Lichen Planus / what is associated? Give a major risk factor.
Etiology is unknown, but there is a genetic component and it is associated with Koebnerization (i.e. scratching could cause an eruption).
Liver disease with HEPATITIS C is a major risk factor.
Histologically, what are Wickham’s striae?
Areas of focal epidermal thickening
What does skin biopsy typically show for lichen planus?
Sawtooth infiltrate of lymphocytes at the dermal-epidermal junction (base of epidermis)
What nail changes does lichen planus cause (vs psoriasis)?
Causes scarring or pterygium formation, often dividing nail plate in two / destroying it.
Vs Psoriasis, Lichen planus has no pitting / salmon color, and much more DESTRUCTIVE nail manifestations
What are the oral manifestations of lichen planus?
- Wickham striae on buccal mucosa -> Destructive lacelike whitish reticular pattern
- Desquamative gingivitis -> Painful gingival erosions
What are the effective treatments for Lichen planus?
- Short courses of systemic steroids and topical high-potency steroids
- Tacrolimus and pimecrolimus
- Longterm immunosuppressive treatment (MTX, AZA) in resistant cases
