In the previous post, we discussed how differentiating atypical papulosquamous diseases can be challenging with the naked eye alone. View previous post

Utilizing a Dermatoscope

For accurate diagnosis, a biopsy or a dermatoscope is used. A dermatoscope can magnify the skin from 10x to over 100x for observation.

Characteristic of Psoriasis - Auspitz Sign

Auspitz, a Czech-born physician in the late 19th century, reported the pinpoint bleeding pattern in psoriasis.

On the background, one can observe erythematous papules covered with white scales. When the scales are peeled off, pinpoint bleeding becomes prominent, which is known as Auspitz sign.

Bernhard, J. D. (1990). Auspitz sign is not sensitive or specific for psoriasis. Journal of the American Academy of Dermatology, 22(6), 1079–1081. doi:10.1016/0190-9622(90)70155-b

The histological characteristic of psoriasis is the appearance of pinpoint bleeding due to elongated dermal papillae in the dermis. It is a useful finding in clinical practice.

Characteristic of Pityriasis Rosea - Collarette Scaling

In pityriasis rosea, scales develop on papules, presenting as collarette scaling.

Chuh, A. A. (2001). Collarette scaling in pityriasis rosea demonstrated by digital epiluminescence dermatoscopy. Australasian Journal of Dermatology, 42(4), 288–290. doi:10.1046/j.1440-0960.2001.00538.x

This appears as a pattern where the central part of the lesion desquamates easily, leaving scales only on the periphery. This characteristic can be observed more clearly with dermatoscopy.

Characteristics of Other Diseases

Plaque psoriasis and nummular eczema also exhibit their respective characteristic scaling patterns. In lichen planus, Wickham striae appear in a branching pattern.

Even without a biopsy, meaningful information can be obtained through dermatoscopy. It is important to become familiar with typical patterns, and a biopsy may be necessary in cases of poor prognosis.