Underlying cause<unk>  is ultimately caused by the presence of a tumor. There is a strong association between the development of<unk>  and malignancy of the tumor. However, it is not uncommon for the tumor to be benign, as in the case of afflictions such as thymoma and Castleman's disease. Only one patient without a tumor has met the diagnostic criteria for<unk> . However, they rapidly reached their demise and it is suggested they may have had an undiagnosed tumor. Mechanism behind display of major symptoms The underlying tumor causes circulating and tissue-bound antibodies to direct themselves against antigens in the plakin family, which are involved in the intracellular attachment structures in various levels of the skin/respiratory tract/membranes (keeping skin tissue together throughout the body). The number of target antigens varies on a case by case basis. The variability is likely what accounts for the different presentations of<unk> . Through immunoprecipitation, target antigens have been found to include desmoglein-3, desmoglein-1, envoplakin, periplakin, desmoplakin 1, desmoplakin 2, and bullous pemphigoid antigen I. The precise mechanism for how tumors are able to induce autoantibodies toward the plakin proteins is unknown. Suggested theories include tumor production of plakin proteins which initiate an autoimmune response against them, and cross-reactivity of tumor antigens and epidermal antigens. Once the molecules that hold the various levels of the membranes together are attacked, they are unable to function properly, and the tissue breaks apart. This is manifested as the associated blistering and lesions of<unk> .
Paraneoplastic pemphigus
IgA pemphigus
Poikiloderma vasculare atrophicans
Pemphigoid nodularis
Mucous membrane pemphigoid
Factitious dermatitis
Vesicular pemphigoid
Bullous pemphigoid