Pemphigus

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Also known as: Pemphigus complex

Introduction

The pemphigus complex is a group of uncommon to rare autoimmune diseases which can occur in different species, but mainly dogs and cats.

Different forms of pemphigus include:

Pemphigus vulgaris
Pemphigus foliaceus
Pemphicus erythematosus
Pemphigus vegetans
Paraneoplastic pemphigus

These diseases lead to epidermal pustule and vesicle formation, and are characterised by an acantholytic process.

Autoantibodies are directed at the interepidermal cell antigens and cement substances and cause epidermal cell separation and cell rounding (acanthocyte formation).

The different forms of disease target different proteins within the skin which leads to variations in the severity and the type of erosion or ulceration.

Trigger factors for the formation of autoantibodies are varied: genetics, hormones, drugs, neoplasia, diet, viruses, stress and physical factors such as burns and UV radiation.

Clinical Features

Pemphigus vulgaris

It is more common in the German Shepherd Dog and the Collie but remains a very rare disease. Males are predisposed, even though females tend to be prone to autoimmune diseases in general, and the age of onset is usually past 6 years old.

The oral cavity is affected in 90% of cases. Disease affects the mucocutaneous junctions, ears, claws, axilla and groin. The paw pads and nails may slough. There are vesicles or bullae, erosions and ulcers.

It is one of the more severe forms of pemphigus and the patients are often ill with anorexia, depression and fever. Secondary bacterial infection is common.

Pemphigus foliaceus

This is the commonest pemphigus disease. It is seen in dogs, cats and horses.

Lesions do not occur in the oral cavity. Primary lesions are transient pustules, but typically, crusts, scales, hair loss, erosions and epidermal collarettes are predominant, and affect the face, ears, feet including footpads and often the groin. Nasal depigmentation is common.

The disease can become generalised and lesions can become widespread over much of the body surface.

The disease may wax and wane, and fever and depression may occur if it is severe.

Pemphigus erythematosus

It is similar to pemphigus foliaceus but lesions are usually confined to the face, especially the nose. There are pustules, crusts, erosions and depigmentation of the nasal planum and the dorsum of the muzzle. The paws and genitals are sometimes affected.

No oral or mucosal lesions are present.

Pemphigus vegetans

This is very rare but has been reported in the dog. It is thought to be a benign version of pemphigus vulgaris. The disease manifests as a vesiculopustular disorder that evolves into verrucous vegetations and papillomatous proliferations, which ooze and are studded with pustules.

Animals are usually otherwise healthy.

Paraneoplastic pemphigus

This is very rare, and is a blistering disease affecting the mucosa and mucocutaneous junctions.

It is seen in conjunction with neoplasias such as the thymoma, thymic lymphoma and splenic sarcoma.

Systemic signs will be present due to the neoplastic process and the skin condition.

Diagnosis

The clinical appearance of the different forms of pemphigus are quite distinct, and these may aid in the diagnosis of the condition.

The most important diagnostic aspects are the history, physical examination and histopathological findings.

Haematology and biochemistry may be helpful in identifying any systemic disease, but abnormalities are uncommon.

Cytology

Cytology of aspirates or impression smears of pustules or crusts are often helpful in the diagnosis.

Pemphigus foliaceus pustules have acanthocytes, which are rounded, darkly stained cells with prominent nuclei, and neutrophils. Bacteria should be absent unless there is a secondary infection.

Acanthocytes are rare in pemphigus vulgaris cases as the clefting is deep.

Bacterial culture should be performed to identify any secondary bacterial infections.

Biopsy

Histopathology is essential for the diagnosis of the pemphigus diseases and will usually allow a diagnosis if taken from multiple intact primary lesions or from the edge of a recent lesion.

Pemphigus vulgaris: there is suprabasilar acantholysis with resultant cleft and vesicle formation. Basal epidermal cells remain attached to the basement membrane zone like a row of 'tombstones'.

Pemphigus foliaceus: there is intragranular or subcorneal acantholysis with cleft and vesicle or pustule formation. Within the vesicle or pustule, acanthocytes may be individual, associated together into rafts, or adherent to the overlying epidermis. Neutrophils or eosinophils may predominate in the vesicles or pustules.

Pemphigus erythematosus: histology is usually identical to pemphigus foliaceus, except that there is often a lichenoid cellular infiltrate of mononuclear cells, plasma cells, and neutrophils or eosinophils or both.

Pemphigus vegetans: there is papillated epidermal hyperplasia, papillomatosis and intraepidermal microabscesses that contain eosinophils and acanthocytes.

Paraneoplastic pemphigus: there is transepidermal pustulation with suprabasilar and superficial acantholysis, prominent apopototic keratinocytes, dermal or submucosal infiltration of lymphocytes, macrophages and plasma cells.

Immunofluorescence

Direct immunofluorescence is helpful but not routinely used due to cost and availability.

All the pemphigus variants show an intercellular pattern of deposition of IgG or complement components. This is often called a 'chicken-wire' pattern of deposition.

Pemphigus erythematosus may show deposition of antigen along the basement membrane in addition to the intercellular findings.

Indirect immunofluorescence is usually negative.

Treatment

Severely affected patients may require antibiotics to control any secondary bacterial infections.

Pemphigus vulgaris

This is a severe disease that is often fatal, and animals may fail to respond to treatment. Aggressive treatment with predisolone and azathioprine should be instituted as soon as a diagnosis is made. Prednisolone with chlorambucil is preferred in cats.

Pemphigus foliaceus

This disease is less severe, but if left untreated, can be fatal. Mild localised lesions can be treated with topical steroids, but more extensive disease usually requires oral prednisolone. More than half the patients require an additional cytotoxic treatment that is synergistic with corticosteroids. This is usually azathioprine or cyclophosphamide in dogs, and chlorambucil in cats. Cyclosporin can also be considered.

Pemphigus erythematosus

This can initially be treated by sun avoidance and topical steroids. In dogs, a combination of tetracycline and niacinamide is effective in up to 25% of cases. Vitamin E or oral glucocorticoids may also be added to the regimen. Topical cyclosporin can also be helpful.

Pemphigus vegetans

Systemic glucocorticoids are usually the treatment of choice.

Paraneoplastic pemphigus

The underlying neoplasia needs to be identified and treated or controlled. Additional treatment may involve systemic glucocorticoids with added cytotoxic agents if necessary.

Monitoring

Patients should be monitored at 2-4 week intervals at first, and medications should be reduced to the minimal dose necessary to control clinical signs. Routine haematology and biochemistry should be performed to identify any organ damage by drug therapy.

The medical therapy has many side effects, which can include: bone marrow suppression, hepatotoxicity, nephrotoxicity, haemorrhagic cystitis or immunosuppression and the development of opportunistic infections.

Prognosis

Prognosis varies with the form of the disease and the severity. Remission is rare for pemphigus vulgaris and foliaceus, and lifelong therapy is usually necessary. Pemphigus erythematosus and vegetans are usually mild diseases which are self-limiting and respond well to therapy.

Secondary bacterial infections contribute to patient morbidity.


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References

Merck and Co (2008) Merck Veterinary Manual Merial

Muller, G. (2001) Small Animal Dermatology Elsevier Health Sciences

Helton Rhodes, K. (2011) Blackwell's five minute veterinary consult: dermatology Wiley-Blackwell




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