This study was supported by Principia Biopharma Inc., a Sanofi company. Conflicts of interestConflicts of interest statements can be found in the Appendix. Data availabilityQualified researchers may request access to patientlevel data and related documents (including, e.g., the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications). Patientlevel data will be anonymized, and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at https://www. clinicalstudydatarequest.com.

Inflammatory markers, particularly hs-CRP and to a lesser extent, fibrinogen and ESR, can be used to assist in assessing disease severity and response to treatment in patients with psoriasis. A combination of selected inflammatory factors (which we term the Index of Psoriasis Inflammation) in combination with PASI might reflect inflammatory status in psoriasis more accurately than each one separately.

Reactive arthritis (ReA) is an immune-mediated seronegative arthritis that belongs to the group of spondyloarthropathies and develops after a gastrointestinal or genitourinary system infection. The condition is considered to be characterized by a triad of symptoms (conjunctivitis, arthritis and urethritis) although a constellation of other manifestations may also be present. ReA is characterized by psoriasiform dermatological manifestations that may resemble those of pustular psoriasis and, similar to guttate psoriasis, is a post-infectious entity. Also, the articular manifestations of the disorder are similar to those of psoriatic arthritis and both conditions show a correlation with HLA-B27. These facts have led several authors to suggest that there is a connection between ReA and psoriasis, listing ReA among the disorders related to psoriasis. However, the pathogenetic mechanism behind the condition is complex and poorly understood. Bacterial antigenicity, the type of host response (i.e. Th1/Th2 imbalance) and various genetic factors (i.e. HLA-B27 etc.) play an important role in the development of the disorder. It is unknown whether all the aforementioned factors are part of a mechanism that could be similar to, or share basic aspects with known psoriasis pathogenesis mechanisms.

Two patients with lichen planus pemphigoides and two with bullous lichen planus were compared. Lichen planus pemphigoides was clinically distinguished by a more generalized lichen planus, more extensive blistering, the need for systemic corticosteroids and by a longer course. The blister of bullous lichen planus was a subepidermal bulla showing degeneration of the epidermal basal layer and other features of lichen planus, whereas in lichen planus pemphigoides the bulla was similar to that of bullous pemphigoid albeit with rather more neutrophils than are usually seen. Direct immunofluorescence was positive in lichen planus pemphigoides and negative in bullous lichen planus. Lichen planus pemphigoides and bullous lichen planus are separate entities: the former is an auto-immune disease precipitated by lichen planus and not related to bullous pemphigoid, the latter is probably not auto-immune but represents the extreme consequence of the lymphoid infiltrate at the dermo-epidermal junction.