Auspitz sign is a feature of
When psoriatic scales are completely scraped off, the basement membrane is exposed and is seen as moist red surface (membrane of Bulkeley) through which dilated capillaries can be seen as red spots.
On further scraping, these capillaries at the tip of elongated papillae are torn leading to multiple bleeding points. This is known as Auspitz sign,
it is attributed to parakeratosis, intracellular edema of epidermal cells, suprapapillary thinning of stratum Malpighi,
elongation of dermal papillae and dilatation and tortuosity of papillary capillaries. PSORIASIS:

Pink Papules/ Plaques/ Pinpoint bleeding (Auspitz sign)/ Physical injury (Koebner phenomenon)
Silver Scale/ Sharp margins
Onycholysis/ Oil Spots
Rete Ridges with Regular elongation
Itching  Arthritis/ Abscess (Munro)
Stratum corneum with nuclei, neutrophils
Immunologic disease
Stratum granulosum absent/ Stratum Spinosum thickening. Plaque Psoriasis
This is the most common and well-recognized form of psoriasis. 2
It is characterized by well-defined raised erythematous papules and plaques with silvery coarse scale.
The distribution is typically symmetric, and sites of predilection include - the extensor surfaces of the extremities, particularly the elbows and knees, sacrum, scalp, nape of the neck, and to a lesser extent trunk, genitalia, face, and ears.
Individuals may present with hyperkeratotic scaling disease localized to the scalp only, making it difficult to discriminate from severe seborrheic dermatitis or tinea capitis. This presentation has been called tinea amiantacea, and requires evaluation to distinguish between these 3 entities.
Additional features of psoriatic plaques include: - Auspitz sign, - Woronoff ’s ring and - Kobner phenomenon
Psoriasis
Lichen planus
Pityriasis alba
All of the above