Psoriasis versus nummular dermatitis. Dermpath made easy.

Psoriasis: a very common condition that affects many body systems. In the skin, psoriasis presents as symmetrical red, well defined, thick silvery scaly plaques.

Psor. is an autoimmune disorder in which one's inflammatory cells (T-cell) attacks their skin. The cause is uncertain; however, genetics, as well as environmental triggers, are likely involved. Enthusiastic (gunner) T-cells causes a rapid turnover of skin, which results in skin thickening, as well as the buildup of the distinctive thick silvery scale. The T-cell also call in other inflammatory cells including neutrophils (essential).

Clues favoring PSORIASIS over spongiotic (nummular) derm:
1. Prominence of vessels in the papillary dermis (often the first thing to show up and serves as a helpful diagnostic clue when psoriasiform acanthosis is not apparent).
2. Regular (even) psoriasiform acanthosis - This is because the T-cells are triggering all areas of the affected skin at the same time; therefore, the epidermis thickens at a relatively even pace throughout.
3. Confluent hyperkeratosis and parakeratosis - continuous without skips (in plaque form).
4. Hypogranulosis (diminished granular layer) and parakeratosis (retained keratinocyte nuclei) - these go hand in hand. When new skin cells get to the surface of the skin too quickly, two things happen 1. there is no time to develop the granular layer. 2. The keratinocyte nuclei are retained in the stratum corneum (see video for more details).
5. Neutrophils in the dermis and in the stratum corneum (T-cells call them). The pattern of neutrophils in stratum corneum - wedged between parakeratosis.
6. suprapapillary plate thinning: vessels just beneath skin surface - Auspitz sign

Nummular dermatitis: Nummular dermatitis is a variant of spongiotic dermatitis in which the lesions start as papules or vesicles but progress to form round or oval scaly plaques. They can be deceptively similar to psoriasis clinically (especially when they are distributed symmetrically and are dry).

Clues favoring SPONGIOTIC DERMATITIS over psoriasis:
1. Irregular psoriasiform hyperplasia: skin cells are not proliferating at an even rate
2. If there is hypogranulosis, it's not widespread or continuous like psoriasis - epidermis is cycling slower than psoriasis
3. impetiginization (bacteria growth): commonly seen in spongiotic/nummular dermatitis
4. a significant number of eosinophils in the dermal infiltrate: exceptions are guttate and drug-induced/associated psoriasis.
5. serum vesicles in epidermis or stratum corneum: psoriasis is usually relatively dry (not weepy)
6. Neutrophils are not a regular part of uncomplicated spongiotic dermatitis. Secondary infection and trauma may cause neutrophils to enter the party but rarely in the same pattern as seen in psoriasis (wedged between stratum corneum parakeratosis)

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Видео Psoriasis versus nummular dermatitis. Dermpath made easy. канала Dr. Michael Lee