Pemphigus

# Overview
Pemphigus is an autoimmune disorder that causes blistering and raw sores on skin and mucous membranes. As with other autoimmune disorders, it is caused when the body's defenses mistake its own tissues as foreign, and attack the cells. This particular autoimmune reaction is sometimes associated with the use of Penicillamine. Pemphigus is derived from the Greek pemphix, meaning bubble or blister.

# Types
There are three types of pemphigus which vary in severity:  pemphigus vulgaris, pemphigus foliaceus, and paraneoplastic pemphigus.
- The most common form of the disorder is pemphigus vulgaris (ICD-10 L10.0). It occurs when antibodies attack Desmoglein 3, a protein that keeps cells bound together.  Thus, cells simply fall apart, causing skin to slough off.  Although pemphigus vulgaris may occur at any age, it is quite rare in children, and most common in the middle aged and elderly.  Sores often originate in the mouth, making eating difficult and uncomfortable. Pemphigus vulgaris often affects people between the ages of 40-60, and mainly of Jewish, Middle Eastern, or Mediterranean descent. Some patients are associated with myasthenia gravis, but it's unusual.
- Foliaceus is the least severe of the three varieties.  Desmoglein 1, the protein that is destroyed by the body's immune system is only found in the top dry layer of the skin, so mouth sores do not occur. Pemphigus foliaceus is characterized by crusty sores that often begin on the scalp, and may move to the chest, back, and face. It is not as painful as pemphigus vulgaris, and is often mis-diagnosed as dermatitis or eczema.
- The least common and most severe type of pemphigus is the neoplastic variety, also known as paraneoplastic pemphigus. This disorder is usually found in conjunction with an already-existing malignancy.  Very painful sores appear on the mouth, lips, and the esophagus. In this variety of pemphigus, the disease process often involves Bronchiolitis obliterans, a fatal destruction of alveoli in lung tissue.  A diagnosis of neoplastic pemphigus may prompt a search for an existing tumor.  Sometimes, the tumor is not malignant.  In these cases, tumor removal may lead to a remission of the pemphigus.  However, any decline in pulmonary function is generally irreversible. With Intravenous Immunoglobulin (IVIG) treatment and aggressive chemotherapy for the underlying lympoma, there are few known survivors of Paraneoplastic Pemphigus with pulmonary involvement (contact information in External Links below).

# Diagnosis
Diagnosis relies on microscopic examination of skin lesion samples. A biopsy of a suspected lesion is taken: a sample of the blistered skin is removed and examined under the microscope to determine if the cells are separated in the manner characteristic of pemphigus.  Unlike in the related pemphigoid, pemphigus manifests as intra-epithelial clefting, meaning the spinous cells of the epithelium break apart, a phenomenon known as acantholysis.  This is because the desmosomes are attacked.  In pemphigoid, the epitheium remains intact, but is entirely "unzipped" from the underlying connective tissue bed, or lamina propria, because the hemidesmosomes are attacked.  Also apparent in pemphigus is a "tombstone appearance" of the basal cell layer and Tzanck cells.
Direct immunoflourescence on the biopsy skin sample can be used to detect desmoglein antibodies in the skin. The presence of these antibodies indicates pemphigus. Indirect immunofluorescence and ELISA can measure desmoglein antibodies in blood serum.

# Treatment
If not treated, pemphigus is fatal, due to overwhelming systemic infection. The most common treatment is the administration of oral steroids, especially prednisone. Recently, there has been great promise of surviving some forms of pemphigus (especially PNP) by using a pooled blood product known as gamma globulin or IVIG. Mild cases sometimes respond to the application of topical steroids. In 2007, a clinical trial including a one-week treatment with Rituximab, a monoclonal chimaeric Anti-CD20-Antibody, approved by the FDA for the treatment of  B-Cell-Non-Hodgkin-Lymphoma and severe cases of rheumatoid arthritis, showed a remission in 18 of 21 otherwise untreatable, severe cases of Pemphigus vulgaris.
All of these drugs may cause severe side effects, so the patient should be closely monitored by doctors. Once the outbreaks are under control, dosage is often reduced, to lessen side effects.
If paraneoplastic pemphigus is diagnosed with pulmonary disease, a powerful cocktail of immune suppressant drugs is sometimes used in an attempt to halt the rapid progression of bronchiolitis obliterans. Some drugs used include solumedrol, ciclosporin, azathioprine, and in rare instances, extremely controlled use of thalidomide in eligible patients. Immune phoresis procedures are also a possible treatment.
If skin lesions do become infected, antibiotics may be used for treatment. In addition, talcum powder is helpful to prevent oozing sores from adhering to bedsheets and clothes.

# Pemphigus in domestic animals
Pemphigus foliaceus has been recognized in pet dogs, cats and horses and is the most common autoimmune skin disease diagnosed in veterinary medicine. Pemphigus foliaceus in animals produces clusters of small vesicles that quickly evolve into pustules. Pustules may rupture, forming erosions or become crusted. Left untreated, pemphigus foliaceus in animals is life-threatening leading to loss of condition and secondary infection.
Pemphigus vulgaris is a very rare disorder described in pet dogs and cats. Paraneoplastic pemphigus has been identified in pet dogs.