Pemphigus vulgaris is a rare chronic blistering skin disease and the most common form of pemphigus. Pemphigus was derived from the Greek word pemphix, meaning blister.[1] It is classified as a type II hypersensitivity reaction in which antibodies are formed against desmosomes, components of the skin that function to keep certain layers of skin bound to each other. As desmosomes are attacked, the layers of skin separate and the clinical picture resembles a blister. These blisters are due to acantholysis, or breaking apart of intercellular connections through an autoantibody-mediated response.[2] Over time the condition inevitably progresses without treatment: lesions increase in size and distribution throughout the body, behaving physiologically like a severe burn.
Before the advent of modern treatments, mortality for the disease was close to 90%. Today, the mortality rate with treatment is in the range 5% to 15%, after the introduction of corticosteroids as primary treatment.[3] Nevertheless, in 1998, pemphigus vulgaris was the fourth most common cause of death due to a skin disorder. It is thus still deemed "potentially fatal".
Pemphigus vulgaris on face
The disease mainly affects middle-aged and older adults between 50 and 60 years old. There has historically been a higher incidence in women.[4]
Signs and symptoms
Pemphigus vulgaris
Pemphigus vulgaris most commonly presents with oral blisters (buccal and palatine mucosa, especially), but also includes cutaneous blisters. Other mucosal surfaces, the conjunctiva, nose, esophagus, penis, vulva, vagina, cervix, and anus, may also be affected. Flaccid blisters over the skin are frequently seen with sparing of the skin covering the palms and soles.[5]
Blisters commonly erode and leave ulcerated lesions and erosions. A positive Nikolsky sign (induction of blistering in normal skin or at the edge of a blister) is indicative of the disease.[5]
Severe pain with chewing can lead to weight loss and malnutrition.[5]
Pathophysiology
Pemphigus is an autoimmune disease caused by antibodies directed against both desmoglein 1 and desmoglein 3 present in desmosomes. Loss of desmosomes results in loss of cohesion between keratinocytes in the epidermis, and a disruption of the barrier function served by intact skin. The process is classified as a type II hypersensitivity reaction (in which antibodies bind to antigens on the body's own tissues). On histology, the basal keratinocytes are usually still attached to the basement membrane leading to a characteristic appearance called "tombstoning". Transudative fluid accumulates in between the keratinocytes and the basal layer (suprabasal split), forming a blister that is easily dislodged when a lateral force is applied, resulting in what is known as a positive Nikolsky's sign.[6] This is a contrasting feature from bullous pemphigoid, which is thought to be due to anti-hemidesmosome antibodies, and where the detachment occurs between the epidermis and dermis (subepidermal bullae). Clinically, pemphigus vulgaris is characterized by extensive flaccid blisters and mucocutaneous erosions. The severity of the disease, as well as the mucosal lesions, is believed to be directly proportional to the levels of desmoglein 3. Milder forms of pemphigus (like foliacious and erythematoses) are more anti-desmoglein 1 heavy.
The disease arises most often in middle-aged or older people, usually starting with a blister that ruptures easily. It can also start with blisters in the mouth. The lesions can become quite extensive.
Diagnosis
Because it is a rare disease, diagnosis is often complicated and takes a long time. Early in the disease patients may have erosions in the mouth or blisters on the skin. These blisters can be itchy or painful. Theoretically, the blisters should demonstrate a positive Nikolsky's sign, in which the skin sloughs off from slight rubbing, but this is not always reliable. The gold standard for diagnosis is a punch biopsy from the area around the lesion that is examined by direct immunofluorescent staining, in which cells are acantholytic, that is, lacking the normal intercellular connections that hold them together. These can also be seen on a Tzanck smear. These cells are basically rounded, nucleated keratinocytes formed due to antibody mediated damage to cell adhesion protein desmoglein.
Pemphigus vulgaris is easily confused with impetigo and candidiasis. IgG4 is considered pathogenic. The diagnosis can be confirmed by testing for the infections that cause these other conditions, and by a lack of response to antibiotic treatment.[7]
An established alternative to steroids are monoclonal antibodies such as rituximab, which are increasingly being used as first-line treatment. In summer 2018, the FDA granted full approval to rituximab for this application, following successful fast track evaluation.[8] In numerous case series, many patients achieve remission after one cycle of rituximab. Treatment is more successful if initiated early on in the course of disease, perhaps even at diagnosis. Rituximab treatment combined with monthly IV immunoglobulin infusions has resulted in long-term remission with no recurrence of disease in 10 years after treatment was halted.[9] This was a small trial study of 11 patients with 10 patients followed to completion.
Due to the successful use of rituximab, an anti-CD20 monoclonal treatment, in managing this disease, other anti-CD20 drugs such as ocrelizumab,[10]veltuzumab,[11] and ofatumumab[12] have been explored as potential treatments.
Key companies in Pemphigus Vulgaris therapeutics include Principia Biopharma, Topas Therapeutics and Argenx BVBA.[citation needed] Rituximab demonstrated superior efficacy compared to mycophenolate mofetil in a Phase III clinical trial, results of which were published in 2021.[13]
Epidemiology
Pemphigus vulgaris is a relatively rare disease that only affects about 1 to 5 people in 1 million in the United Kingdom, with an incidence of 1-10 cases per 1 million people across the world. There is an estimated prevalence of 14,000+ cases in the United States[14] and 42,400+ in the seven major markets (US, UK, Japan, Germany, France, Italy, Spain) which is five times as prevalent as Pemphigus foliaceous.[citation needed]
Cases of P. vulgaris usually don't develop until after the age of 50 or so. The disease is not contagious which means it cannot be spread from person to person.[15] In 2012, Israeli researchers indicated they had identified a genetic cause for the disease, which they indicated as 40 times more likely to afflict Jews compared to other demographic groups.[16]
The data pool is small for rare diseases. Some sources claim females being more affected by the disease, for others men and women are equally affected. The patient advocacy organisation NORD sees people of many different cultures and racial backgrounds simllarly affected, but with a prevalence for Ashkenazi Jews, people of Mediterranean, North Indian and Persian descent.[17] There has been no found difference in the rate of disease when looking at socioeconomic factors as well.[14] If left untreated, 8 of 10 people with the disease die within a year with a cause of death being infection or loss of fluids, which is very common for raw, open sores that are characteristic of P. vulgaris. With treatment, only about 1 in 10 people with the disease die, either from the condition, or side effects of the medicine.[15]
An effect of the disease being so rare is that there is not enough evidence to prove that the treatments currently being used are actually as effective as they could be. Doctors are trying to find effective steroid-sparing agents to use in the treatment, to decrease the side effects of long term steroid treatment. The small amount of case numbers make it hard to test statistical significance between the affected and the control groups when testing if these types of systematic treatments are effective.[18]
Research
Research into using genetically modified T-cells to treat pemphigus vulgaris in mice was reported in 2016.[19][20] Rituximab indiscriminately attacks all B cells, which reduces the body's ability to control infections. In the experimental treatment, human T cells are genetically engineered to recognize only those B cells that produce antibodies to desmoglein. In PV, autoreactive B cells produce antibodies against Dsg3, disrupting its adhesive function and causing skin blistering. By expressing Dsg3 on their surfaces, the CAAR-T cells lure those B cells in and kill them. The Dsg 3 CAAR-T cells eliminated Dsg3-specific B cells in lab dishes and in mice, the researchers reported at the time.
A desmosome, also known as a macula adherens, is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. Desmosomes are one of the stronger cell-to-cell adhesion types and are found in tissue that experience intense mechanical stress, such as cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelia.
Pemphigus is a rare group of blistering autoimmune diseases that affect the skin and mucous membranes. The name is derived from the Greek root pemphix, meaning "blister".
Rituximab, sold under the brand name Rituxan among others, is a monoclonal antibody medication used to treat certain autoimmune diseases and types of cancer. It is used for non-Hodgkin lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis, granulomatosis with polyangiitis, idiopathic thrombocytopenic purpura, pemphigus vulgaris, myasthenia gravis and Epstein–Barr virus-positive mucocutaneous ulcers. It is given by slow intravenous infusion.
Staphylococcal scalded skin syndrome (SSSS) is a dermatological condition caused by Staphylococcus aureus.
Bullous pemphigoid is an autoimmune pruritic skin disease that typically occurs in people aged over 60, that may involve the formation of blisters (bullae) in the space between the epidermal and dermal skin layers. It is classified as a type II hypersensitivity reaction, which involves formation of anti-hemidesmosome antibodies, causing a loss of keratinocytes to basement membrane adhesion.
Nikolsky's sign is a clinical dermatological sign, named after Pyotr Nikolsky (1858–1940), a Russian physician who trained and worked in the Russian Empire. The sign is present when slight rubbing of the skin results in exfoliation of the outermost layer. A typical test would be to place the eraser of a pencil on the roof of a lesion and spin the pencil in a rolling motion between the thumb and forefinger. If the lesion is opened, then the Nikolsky's sign is present/positive.
Hailey–Hailey disease (HHD), or familial benign chronic pemphigus or familial benign pemphigus, was originally described by the Hailey brothers in 1939. It is a genetic disorder that causes blisters to form on the skin.
The desmogleins are a family of desmosomal cadherins consisting of proteins DSG1, DSG2, DSG3, and DSG4. They play a role in the formation of desmosomes that join cells to one another.
Desmoglein-1 is a protein that in humans is encoded by the DSG1 gene. Desmoglein-1 is expressed everywhere in the skin epidermis, but mainly it is expressed in the superficial upper layers of the skin epidermis.
Desmoglein-3 is a protein that in humans is encoded by the DSG3 gene. In the skin epidermis Desmoglein-3 is expressed in the basal lower layers of the epidermis, and dominates in terms of expression on mucosal surfaces compared to Desmoglein-1.
Pemphigoid is a group of rare autoimmune blistering diseases of the skin and mucous membranes. As its name indicates, pemphigoid is similar in general appearance to pemphigus, however unlike pemphigus, pemphigoid does not feature acantholysis, a loss of connections between skin cells.
Discoid lupus erythematosus is the most common type of chronic cutaneous lupus (CCLE), an autoimmune skin condition on the lupus erythematosus spectrum of illnesses. It presents with red, painful, inflamed and coin-shaped patches of skin with a scaly and crusty appearance, most often on the scalp, cheeks, and ears. Hair loss may occur if the lesions are on the scalp. The lesions can then develop severe scarring, and the centre areas may appear lighter in color with a rim darker than the normal skin. These lesions can last for years without treatment.
Dermatitis herpetiformis (DH) is a chronic autoimmune blistering skin condition, characterised by intensely itchy blisters filled with a watery fluid. DH is a cutaneous manifestation of coeliac disease, although the exact causal mechanism is not known. DH is neither related to nor caused by herpes virus; the name means that it is a skin inflammation having an appearance similar to herpes.
Pemphigus foliaceus is an autoimmune blistering disease of the skin. Pemphigus foliaceus causes a characteristic inflammatory attack at the subcorneal layer of epidermis, which results in skin lesions that are scaly or crusted erosions with an erythematous (red) base. Mucosal involvement is absent even with widespread disease.
Pemphigus erythematosus is a localized form of pemphigus foliaceus with features of lupus erythematosus.
Paraneoplastic pemphigus (PNP) is an autoimmune disorder stemming from an underlying tumor. It is hypothesized that antigens associated with the tumor trigger an immune response resulting in blistering of the skin and mucous membranes.
Psoriatic erythroderma represents a form of psoriasis that affects all body sites, including the face, hands, feet, nails, trunk, and extremities. This specific form of psoriasis affects 3 percent of persons diagnosed with psoriasis. First-line treatments for psoriatic erythroderma include immunosuppressive medications such as methotrexate, acitretin, or ciclosporin.
Mucous membrane pemphigoid is a rare chronic autoimmune subepithelial blistering disease characterized by erosive lesions of the mucous membranes and skin. It is one of the pemphigoid diseases that can result in scarring.
Anti-AQP4 diseases, are a group of diseases characterized by auto-antibodies against aquaporin 4.
Autoimmune skin diseases occur when the immune system of an infected animal attacks its own skin. In dogs, autoimmune skin diseases are usually not detected until visible symptoms appear, which differs from detection in humans who are able to verbally express their concerns. Genetics, nutrition, and external environmental factors all collectively contribute to increasing the probability an autoimmune skin disease occurring. The severity of symptoms varies based on the specific disease present and how far it has progressed. Diagnosis often requires the onset of visible symptoms and for a biopsy to be performed. For many diseases, the condition itself cannot be cured, but a veterinarian can prescribe medications and other forms of treatment to help manage the symptoms of the dog.
↑ de-la-Rosa-Fernández E, Loizate-Sarrionandia I, González-Rodríguez J, Herrero-Moyano M, Fernández-de-Misa-Cabrera R, Suárez-Hernández J (April 2023). "Ocrelizumab, an alternative to rituximab in refractory pemphigus vulgaris management". Journal of the European Academy of Dermatology and Venereology. 37 (9): e1104–e1106. doi:10.1111/jdv.19133. PMID37102356. S2CID258355167.
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