Dr. Alina G. Bridges discusses the various ways in which pemphigus and pemphigoid present and the role of immunofluorescence testing as part of the diagnostic approach.
Alina G. Bridges, DO, FAAD, Director, Dermatopathology, Donald and Barbara Zucker School of Medicine, Hofstra School of Medicine, New Hyde Park, NY
“We use immunofluorescence not only in the diagnosis of autoimmune mucocutaneous blistering disorders like pemphigus and pemphigoid, but we can also use it the diagnosis of autoimmune connective tissue diseases, vasculitis, vasculopathy, porphyria, pseudoporphyria, and lichenoid dermatoses,” said Alina G. Bridges, DO, FAAD, who presented “Pemphigus and Pemphigoid Disorders” in the session entitled A Practical Approach to Direct Immunofluorescence at the 2023 American Academy of Dermatology (AAD) Annual Meeting.
“The big overview on using immunofluorescence to diagnose these diseases is that you have to correlate the clinical presentation with the histopathology and then confirm the diagnosis by the immunofluorescence testing, which can be tissue-based or serum-based. Direct immunofluorescence is a tissue-based assay.”
Pemphigus and pemphigoid do not always present with tell-tale blisters, ulcers, and erosions, said Dr. Bridges.
“…it can look like almost any inflammatory dermatosis.”
It can look like psoriasis or dermatitis, or present with severe itching and secondary lesions from scratching, she said.
“These disorders should be included in the workup of erythroderma and generalized pruritis.”
According to Dr. Bridges, these conditions are great mimickers clinically and histopathologically.
“These patients can also have severe presentations that can mimic Stevens Johnson Syndrome and toxic epidermal necrolysis as well as erythroderma. So their skin can be diffusely red and scaly.”
They can have pustules, hives, or annular lesions, she said.
“And sometimes you may not see inflammatory cells like eosinophils in the biopsy, so that histopathology sometimes is not very specific. And so you have to have a high index of suspicion for these disorders. They always need to be on your radar.”
And as such, immunofluorescence testing is recommended, said Dr. Bridges.
Immunofluorescence Testing
“The direct immunofluorescence is a skin biopsy that’s done in the office and that’s where errors can occur because sometimes clinicians don’t know where to biopsy correctly to diagnose pemphigus and pemphigoid.”
The biopsy needs to be taken from immediately adjacent, noninflamed normal skin, not from the involved area in these blistering conditions, said Dr. Bridges.
“In this case, you have to biopsy uninvolved or perilesional skin, and you have to know how to submit the biopsy because you can’t put it in formalin.”
You can use Michel’s media or normal saline. Other options are to send it to the lab in liquid nitrogen or using Zeus medium, said Dr. Bridges.
“We look at different patterns in the dark with a immunofluorescence microscope. The specimens have a cell surface fluorescence pattern or basement membrane zone pattern or a combination of both.”
Next, serum-based testing using indirect immunofluorescence and ELISA antibody testing is recommended to confirm the diagnosis, said Dr. Bridges.
“Typically, we do that with salt split skin, monkey esophagus substrate, and sometimes rat bladder substrate to confirm the diagnosis. And we also have target antigens that we can test for with ELISA kits, so we can test for desmogleins 1 and 3 in pemphigus and BP 180 and 230 in pemphigoid.
It is important that we go beyond direct immunofluorescence testing, she said.
“…it’s important because you need to recognize when to consider these blistering disorders in your clinical and histopathologic differential diagnosis and how to correctly establish the correct diagnosis using tissue- and serum-based testing. You need to consider these diagnoses in your differential diagnosis especially in atypical presentations and know how to appropriately evaluate these patients to establish the diagnosis so that the diagnosis is not delayed and so that you can appropriately manage the patient.”
The longer these conditions remain undiagnosed, the longer it can take to get them under control and the higher the initial antibody titers at the time of diagnosis.
“That’s why we test the serum. The serum-based testing can sometimes be positive when the direct immunofluorescence is negative. Serum-based testing not only plays a role in diagnosis but plays a role is pathogenesis, disease monitoring, prognosis, and response to therapy. The antibody titers correlate with disease activity and we can use them to monitor the patient’s response to therapy. The higher the antibody titers are, typically the more severe the disease, and the longer it can take to get the disease under control.”
Prior to prednisone availability, patients would die from pemphigus because severe oral involvement prevented them from eating and infection, said Dr. Bridges.
In addition to skin involvement, “these patients can have any of their mucous membrane surfaces involved: mouth, eyes, genital area, and esophagus. It’s extremely distressing and painful for many of these patients. They can also have nail involvement.”
According to Dr. Bridges, it can take years of experience to recognize when to consider these diseases in your clinical and histopathological differential diagnosis and the type of workup that needs to be performed.
“I would say that the greatest pitfall is to not do immunofluorescence testing.”