Eczematous Diseases
Basic Information on Eczematous Diseases
- basic pathologic change common to most eczemas = Spongiosis
Ø inter-cellular edema between keratinocytes
- exocytosis – inflammatory cells migrate into the epidermis
- Acanthosis – thickened Malphigian (spinous) layer in the epidermis
- Hyperkeratosis – thickened stratum corneum
- Lichenified – chronically thickened skin
- Lichen Simplex Chronicus – when the skin gets very thick and lichinified
- Parakeratosis – retained nuclei seen in the stratum corneum in diseases
where there is something wrong with the epidermis
- Neutrophils are predominant in ONLY A FEW skin conditions
- All of the eczemas, even when acute, consist of predominantly of lymphocytes and histiocytes
- Acute contact dermatitis – mononuclear cells
- Psoriasis – neutrophils in the stratum corneum
- Eczema – group of diseases 1o differentiated by their location
- Dermatitis – synonym for eczema (frequently used as one); other – any inflammation of the skin
Specific Eczematous Diseases
Atopic Dermatitis
- patients have numerous ALLERGIES
- FAMILIAL predisposition
- Serum IgE is often elevated
- Onset in childhood after 3 months
- Pruitis is usually severe
- 90% “outgrow” the disease by adolescence
- 2o infections of the skin are common
- can occur anywhere (infants – head, diaper area, and extremities)
- Patients may have prominent infraorbital folds (Dennie’s Lines) or linear markings on the palms
Seborrheic Dermatitis
- areas of involvement – prominent sebaceous gland activity areas (scalp, face, chest…)
- occurs most commonly in early infancy and after puberty
- Treatment: anti-seborrheic shampoos such as sulfur salicylic acid, coal tar, selenium sulfide, or zinc pyrithione. Also used are topical corticosteroids
Stasis Dermatitis
- occurs on the lower legs; older individuals
- 2o to peripheral venous insufficiency
Contact Dermatitis
- 2 types
1) Allergic contact dermatitis
Ø occurs from delayed hypersensitivity (Type IV) reactions to a topical allergen
Ø occurs 2-3 days after contact
Ø most common example – poison ivy – others – neomycin, rubber, nickel…
Ø tends to be more acute vesicular and brighter red than the other eczemas
2) Irritant contact dermatitis
Ø more chronic, drier, and scaly with less vesiculation than the allergic
Ø mechanism – simple irritation
Ø acids, alkalis, solvents, detergents
Nummular Eczema
- coin-shaped patches of eczema on the extremities
- frequently mistaken for tinea
Dishydrotic Eczema
- occurs on the hands and feet (especially the palms, soles, and sides of the fingers
- If acute – may be deep-seated vesicles (resembles tapioca pudding)
- Patients: usu professional people under stress
- Often accompanied by hyperhydrosis
Neurodermatitis
- chronically-scratched eczema
- occurs in “neurotic” or “nervous” persons
- no other cause is apparent
Asteotic (Xerotic) Eczema
- asteotic = no fat (no oil on skin)
- dry skin
- most common in elderly on the extremities
Fungus – Candida, Malassezia furfur, & Tinea infections
Tinea infections
- tinea = dermatophyte fungus infections of the skin
Ø 3 genera
1) Micro-sporum
2) Epidermophyton
3) Trichophyton
- PAS stain stains fungus pink
- GMS stain stains fungus black
- KOH prep – scales on slide, KOH dissolves the keratinocytes and the thick fungal walls become more visible.
- “if it scales, scrape it”
- tinea capitis, tinea pedis, tinea cruris, tinea corporis, tinea manuum
Candida Albicans infections
- yeast (not considered a dermatophyte)
- normal flora in the mouth, vagina, and GI tract
- “thrush”
- Identified on KOH wet prep
- rashes on the skin can be eczematous but may also produce satellite pustules
Ø these pustules are vesicles under the stratum corneum and are filled with neutrophils
Malassezia furfur (also called Pityrosporum orbiculare)
- grows only in follicles of the skin as normal flora
- Clinical disease: when yeast proliferates and forms hyphae and small clusters of spores (spaghetti and meatballs)
- Clinical disease called – Pityriasis versicolor or tinea versicolor
- The disease varies in color from shitish to reddish to brownish
- Scaly like an eczema and usually involves the trunks of young adults
Mycosis Fungoides
- T cell lymphoma of the skin that starts out as an eczematous eruption
- The large patches in the disease fail to respond to the topical steroid therapy normally given for eczema
- “mycosis fungoides” – refers to the fungating, oozing tumors that occur in the disease in the late stages
- has NOTHING to do with fungus
- Biopsy: malignant T cells with cerebriform nuclei invading the skin.
Tags: Acanthosis, Epidermophyton, exocytosis, Hyperkeratosis, Lichen Simplex Chronicus, Lichenified, Micro-sporum, Neurodermatitis, Neutrophils, Parakeratosis, psoriasis, Tinea infections, Trichophyton
