**2.5 Erythrodermic psoriasis**

Erythroderma is a life-threatening condition, which is defined as desquamation and erythema of more than 90% of body surface area [30]. Erythrodermic variant of psoriasis (**Figure 26**) generally occurs due to poor control of disease, withdrawal of anti-psoriatic treatments, triggering drug intake, underlying systemic infections or

#### **Figure 25.**

*Milky globules on reddish background. Globules are non-follicular (red circle). Note the absence of vessels. Anatomical localization: Trunk (10).*

*Dermoscopic Differential Diagnosis of Psoriasis DOI: http://dx.doi.org/10.5772/intechopen.103004*

**Figure 26.** *Desquamation and erythema of all body surfaces.*

conditions [31]. Clinical clues for erythrodermic psoriasis diagnosis are known history of psoriasis, psoriatic nail changes, presence of psoriatic arthritis. However, if none of the mentioned features is present, dermoscopy could be a game-changer.

### *2.5.1 Dermoscopy of erythrodermic psoriasis*

Dermoscopic features of erythrodermic psoriasis are the same as other psoriasis variants. Regularly distributed dotted vessels on a reddish background, and patchy white scales are seen (**Figure 27**) [32].

#### *2.5.2 Dermoscopic differential diagnosis of erythrodermic psoriasis*

Dermoscopic differential diagnosis of erythrodermic psoriasis includes dermatosis that can present with erythroderma such as atopic dermatitis, mycosis fungoides, and pityriasis rubra pilaris (Pityriasis rubra pilaris will not be mentioned because it was discussed above.)

Dermoscopic examination of atopic dermatitis shows typical dermatitis features. Yellowish globules (corresponding to sero-crusts) and patchy distributed dotted vessels on a pinkish background are demonstrative (**Figure 28**) [32].

Dermoscopic features of erythrodermic mycosis fungoides are a combination of linear and dotted vessels on a pale pinkish background (**Figure 29**) [32]. Some short linear vessels may be curved and named as "spermatozoon-like" vessels.

**Figure 27.** *Regularly distributed dotted vessels and white scales. Anatomical localization: Lower extremity (20).*

#### **Figure 28.**

*Yellow globules, patchy distributed dotted vessels. Background is slightly pinkish. Tiny white scales are also present. Tiny white scales correspond to desquamation areas. Anatomical localization: Trunk (10).*

#### **Figure 29.**

*Linear, serpiginous, and dotted vessels on pinkish background. Tiny white scales correspond to desquamation areas. Anatomical localization: Trunk (10).*


#### **Table 4.**

*Dermoscopic features of erythrodermic psoriasis and its differentials.*

Dermoscopic features of erythrodermic psoriasis and its differentials are summarized in **Table 4**.
