**2.4 Pustular psoriasis**

Pustular psoriasis is a rare clinical variant of psoriasis, which is characterized by sterile pustules on an erythematous skin (**Figure 23**). It could be either local or generalized [26]. In generalized pustular psoriasis, concomitant fever, malaise, dehydration may also be present [27].

#### **Figure 22.**

*Wickham striae in "radial streaming" pattern (red circle) and "starry sky" pattern (blue circle). Dotted vessels surround Wickham striae in a patchy arrangement. Anatomical localization: Intermammary (10).*


#### **Table 3.**

*Dermoscopic features of inverse psoriasis and its differentials.*

**Figure 23.** *Small pustules and lake of pus on erythematous background.*

## *2.4.1 Dermoscopy of pustular psoriasis*

Dermoscopic features of pustular psoriasis are characterized by regularly distributed dotted vessels with milky globules (corresponding to sterile pustules) on reddish background (**Figure 24**) [28]. Attention should be paid on non-follicular localization of pustules. Typical vascular structures are seen. Nonspecific yellow crust may be seen. Dermoscopic features are same in both localized and generalized subtypes.

#### *2.4.2 Dermoscopic differential diagnosis of pustular psoriasis*

Dermoscopic differential diagnosis of pustular psoriasis should be done with acute generalized exanthematous pustulosis (AGEP). In life-threatening clinical conditions such as generalized pustular eruptions, rapid and right diagnosis is essential, and dermoscope is very helpful at that point. In both pustular psoriasis and AGEP,

#### **Figure 24.**

*Milky globules and regularly distributed dotted and bushy vessels on reddish background in pustular psoriasis. Anatomical localization: Trunk (10).*

pustules are sterile, disseminated, may coalesce, and be non-follicular. Thereby, we cannot distinguish these two situations by their clinical view only. In dermoscopic examination of both pustular psoriasis and AGEP, non-follicular milky globules on reddish background are seen [28]. Discriminately, in pustular psoriasis we see regularly distributed dotted vessels (**Figure 24**). In dermoscopic examination of AGEP, background is usually pinkish and vascular structures are absent (**Figure 25**) [29].
