In order to diagnose<unk> , several tests may be performed. Initially, samples are obtained via skin biopsy for routine microscopy and direct immunofluorescence (DIF) testing. The skin sample needs to be obtained from an unaffected area adjacent to a lesion. Testing in more detail follows depending on the results from the DIF. Prompt diagnosis of<unk>  is crucial due to the high mortality rate of the disease. Camisa and Helm revised the original criteria from Anhalt et al. into major and minor signs indicating<unk> : Major: *Polymorphic mucocutaneous eruption *Concurrent internal tumor *Serum antibodies with a specific immunoprecipitation pattern Minor: *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<unk> . 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<unk> . 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. Epidermolysis Bullosa, Epidermolysis Bullosa Acquisita, Erythema Multiforme, Lichen Planus,<unk>  vulgaris, Stevens–Johnson syndrome and toxic epidermal necrolysis.<unk>  is most commonly mistaken for<unk>  vulgaris, due to the extreme similarities of the lesions that develop. However, the difference lies in the specificity of the autoreactive antibodies in each case.
Paraneoplastic pemphigus
IgA pemphigus
Poikiloderma vasculare atrophicans
Pemphigoid nodularis
Mucous membrane pemphigoid
Factitious dermatitis
Vesicular pemphigoid
Bullous pemphigoid