# Understanding the Intricate Pathophysiology of Psoriasis and Related Skin Disorders
## 4 Sporiasis and Associated Dermatologic Disorders
This disease is characterized by the presence of autoantibodies targeting a 200-kDa dermal protein located in the lower lamina lucida of the basement membrane zone. Notably, approximately 90% of sera from patients with anti-p200 pemphigoid exhibit immunoreactivity to the \(\gamma\)-1 chain of laminin. Consequently, some researchers have proposed renaming this condition to anti-laminin \(\gamma\)1 pemphigoid [30]. The mean age of patients with anti-laminin \(\gamma\)1 pemphigoid is 65.5 years, with a range spanning from 5 to 94 years, which is notably younger compared to individuals with BP. Patients with anti-lamy1 pemphigoid typically present with bullae, urticial plaques, and occasional pruritus, which can resemble other subepidermal autoimmune bullous diseases, particularly BP. Mucosal lesions have been reported in 20% to 40% of these patients [31]. It is known that anti-lamy1 pemphigoid patients often have pre-existing psoriasis. A recent systematic review reported a prevalence of psoriasis in 56.0% of Japanese patients with anti-lamy1 pemphigoid, compared to 6.4% in non-Japanese cases. Given this strong association between anti-lamy1 pemphigoid and psoriasis, it is reasonable to consider the potential development of anti-lamy1 pemphigoid in psoriasis patients who present with bullae. However, the mechanisms underlying the frequent coexistence of these two conditions and the specific clinical characteristics of these patients remain inadequately understood [31]. The association between pemphigus and psoriasis was only recently suggested by a few epidemiological studies. Three cross-sectional studies examined the prevalence of psoriasis among patients with pemphigus compared to control groups. A meta-analysis of these studies found a pooled odds ratio (OR) of 3.5 for psoriasis in patients with pemphigus. Pemphigus refers to a group of rare, potentially serious autoimmune blistering disorders that affect the intraepidermal layer of the skin. Clinically, it presents with vesicles and erosions on the skin and mucous membranes, which can significantly impact the patient's quality of life and lead to increased morbidity and mortality. The condition's pathogenesis involves the production of immunoglobulin G (IgG) autoantibodies targeting desmoglein 3 and desmoglein 1, which are cadherin-type cell-cell adhesion molecules in the epidermis. There are fewer reports of pemphigus foliacus being associated with psoriasis. Studies indicate that patients with psoriasis are more than three times as likely to develop new-onset pemphigus foliacus compared to the control group. Additionally, across all published studies, the incidence of comorbid psoriasis in patients with pemphigus foliacus is 2.4%. The most commonly associated types of pemphigus foliacus with psoriasis are pemphigus erythematosusous, followed by pemphigus vulgaris, IgA pemphigus, and herpes-like pemphigus. The following hypotheses have been proposed to explain their co-occurrence, as seen in Table 3[32]. Nevertheless, the pemphigus group is associated less frequently with psoriasis, compared to the autoimmune subepidermal bullous diseases group [31]. Connective tissue diseases, including systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and dermatomyositis (DM), also display a complex relationship with psoriasis [32]. Both psoriasis and SLE belong to a group of immune-mediated inflammatory diseases (IMIDs), but their coexistence is very rare. Studies are limited to case series and small, single-center retrospective studies. The prevalence of SLE in patients with psoriasis has been reported to be estimated at 0.69%, while psoriasis occurs in 1.1% of patients who had previously been diagnosed with lupus, which is rarer than in the general population [33]. The types of psoriasis were plaque-type (87.3%), pustular type (4.8%), scalp psoriasis (7.9%), and psoriatic arthritis (PsA) (1.6%), suggesting that the co-existence of SLE and PsA is rare.