This is attributed to the effects of the tumor combined with the negative side effects of the medication administered to treat PNP.Roughly 1/3 of the deaths from PNP stem from pulmonary insufficiency which is brought about by the action of PNP on the respiratory mucosa. It manifests as dyspnea and progresses to bronchiolitis obliterans (non-reversible obstructive lung disease) via an unknown mechanism. Risk Factors
As PNP is ultimately caused by the presence of a tumor, it is not contagious. There is no known way to predict who will become afflicted with it. Patients with cancer are therefore a group at risk. Although PNP has been known to affect all age groups, it is more likely to afflict middle-aged to older patients. Recent research
The Development of ELISA testing for specific diagnosis of PNP was released in 2009. The research focuses on the specific determination of autoantibodies involved in the mechanism of PNP. Specifically, antibodies against envoplakin and periplakin were being investigated. Further use of ELISA testing on these antibodies confirmed the presence of anti-envoplakin and anti-periplakin autoantibodies in patients with PNP.Further research in 2013 outlined the various types of assays that could be used to determine which antibodies were involved in PNP. Demonstration of certain antibodies in the serum was named as the basis for diagnosis of PNP.
into major and minor signs indicating PNP:Major:

Polymorphic mucocutaneous eruption
Concurrent internal tumor
Serum antibodies with a specific immunoprecipitation patternMinor:

Histologic evidence of acantholysis (loss of intercellular connections leading to breaking apart of the skin; lesion)
Direct immunofluorescence showing intercellular and basement membrane staining
Indirect immunofluorescence staining with rat bladder epithelium

Microscopy
Microscopy of the skin sample obtained from the biopsy is used to detect the presence of cleavage within the dermis, epidermal acantholysis (breaking apart of the skin), dyskeratotic keratinocytes and vacuolar changes in the layers of the skin, interfacial dermatitis, and epidermal exocytosis. Presentation of these characteristics suggests PNP. Direct immunofluorescence testing
The presence of Immunoglobulin G, A, or M in the epidermis is normal. Detection in other locations such as intercellular and areas below the epidermis (subepidermal), as well as along the dermoepidermal junction (area that joins the epidermis and dermis), suggests paraneoplastic pemphigus. Follow-up tests for confirmation
Indirect immunofluorescence (IDIF)
Patients with high concentration of antibodies show intercellular, intraepidermal antibodies as well as along the dermoepidermal junction. Patients with low concentration of antibodies only present with them inside the cells (intercellular).If the results are negative, perform the additional assays regardless. Cases have been confirmed that reported with initial negative DIF and IDIF tests. Assays
Immunoprecipitation, immunoblotting and enzyme-link immunosorbent assay (ELISA)
Poot et al. 2013 determined that immunoprecipitation for antibodies against envoplakin and periplakin or alpha2-macroglobulin-like–1 is the most sensitive test. However, alpha2-macroglobulin-like-1 can also be detected in patients with toxic epidermal necrosis. Similar diseases with overlapping symptoms
Bullous Pemphigoid, Cicatricial Pemphigoid, Drug Eruptions.