*2.3.1 Dermoscopy of inverse psoriasis*

Dermoscopic features of inverse psoriasis are characterized by regularly distributed dotted vessels on reddish background (**Figure 21**). In contrast with other variants, scales are absent. Absence of scales enhances visualization of vascular structures. Consequently, dermoscopic differential diagnosis of flexural dermatosis mainly leans on evaluation of vascular structures.

**Figure 20.** *Coalesced erythematous papules located in the glans penis and penile dorsum.*

**Figure 21.** *Regularly distributed dotted vessels on pinkish background. Anatomical localization: Inframammary (10).*

### *2.3.2 Dermoscopic differential diagnosis of inverse psoriasis*

Differential diagnosis of inverse psoriasis should be done with skin diseases, which present with erythematous patches/plaques in flexural and genital areas. Mechanical intertrigo, seborrheic dermatitis, lichen planus inversus, and fungal/bacterial infections may count as differential. Because no clear dermoscopic features have been defined for mechanical intertrigo and flexural infections, we will discuss dermoscopic features of seborrheic dermatitis and lichen planus inversus under this topic.

The main dermoscopic features of seborrheic dermatitis of flexural areas are irregularly distributed linear, blurry vessels [22]. As we mentioned before, we do not see classical yellowish scales of seborrheic dermatitis in flexuras.

When we review the literature so far, there are only three reports about dermoscopic features of lichen planus inversus. In all of these reports, dermoscopic features of only pigmented variant of lichen planus inversus were evaluated and defined as diffuse brown patches containing multiple granular gray-brown dots [23–25]. In our clinical practice, we see non-pigmented lichen planus inversus more than pigmented subtype. According to our dermoscopic experience, Wickham striae, which is seen in lichen planus inversus, tends to be in "starry sky" or "radial streaming" pattern rather than reticular pattern. Background is usually pinkish or violaceous. Dotted vessels usually encircle Wickham striae (**Figure 22**).

Dermoscopic features of inverse psoriasis and its differentials are summarized in **Table 3**.
