**3. Predisposing factors**

PV is a polygenic disease and low titers of disease-associated autoantibodies have been demonstrated in first-degree healthy relatives of patients with pemphigus [4, 5]. For many years, a strong association between Class II Human leukocyte antigen (HLA) polymorphism and pemphigus vulgaris has been known, with the highest incidence seen among Ashkenazi Jews. The interethnic variability in the occurrence of pemphigus vulgaris has been associated with genetic susceptibility. Associated HLA polymorphisms are HLA-DRB1∗ 0402, HLA-DRB1∗14, HLA-DQB1∗ 0503, HLA-DRB1∗ 0302 and HLA-DRB1∗ 08. Of these, HLA-DRB1∗ 0402, HLA-DRB1∗ 14 and HLA-DRB1∗ 08 have a statistically significant relationship with the incidence of pemphigus vulgaris [6].

Pemphigus vulgaris is associated with a variety of diseases, including other autoimmune disorders, psoriasis, neurological and psychiatric disorders, and some malignancies [7]. In addition, environmental factors may also be effective in initiating and maintaining the disease process. These causes include medications, viral infections, physical agents, contact allergens, vaccines, diet and psychological factors (**Table 1**) [8–11].


#### **Table 1.**

*Trigger factors for pemphigus vulgaris.*
