Pemphigus Vulgaris

Detailed Overview

The disease is caused by IgG autoantibodies targeting desmogleins, which are critical adhesion proteins in desmosomes that hold epidermal cells together. This causes acantholysis (loss of cell-to-cell adhesion). Mucosal involvement (especially the oral cavity) is almost universal and often precedes skin lesions by months. Prior to the advent of systemic corticosteroids, PV was almost uniformly fatal due to fluid loss and sepsis.

Epidemiology & Demographics

Rare, with an incidence of 0.1 to 0.5 per 100,000 annually. It most commonly affects individuals between 40 and 60 years of age. Higher prevalence in people of Ashkenazi Jewish, Mediterranean, or Indian descent.

Etiological Mechanism

An autoimmune reaction where B cells produce IgG antibodies against epidermal desmogleins. Genetic predisposition (specific HLA class II alleles) is strongly implicated.

Primary Causes

Production of anti-Desmoglein 3 (Dsg3) and anti-Desmoglein 1 (Dsg1) autoantibodies. Certain drugs (penicillamine, captopril) can rarely induce pemphigus.

• Genetics: Strong association with HLA-DRB1*04:02 and HLA-DQB1*05:03 alleles.
• Medications: Thiol-containing drugs (e.g., Penicillamine) can cause drug-induced PV.
• Other autoimmune diseases: Co-occurrence with myasthenia gravis or thymoma is rare but recognized.

IgG autoantibodies bind to the extracellular domain of Desmoglein 3 (found in the lower epidermis and mucosa) and Desmoglein 1 (found in the upper epidermis). This binding sterically hinders desmosome formation or triggers intracellular signaling that depletes desmosomes. This results in 'acantholysis', where keratinocytes detach from one another. Because the basal layer remains attached to the basement membrane via hemidesmosomes (which are not targeted), a 'tombstone row' appearance is seen histologically. The resulting blister is superficial (suprabasal) and therefore very fragile.

Characteristic Clinical Presentation

• Oral Erosions: Severe, painful mouth sores causing difficulty eating or drinking. Often the first symptom.
• Flaccid Blisters: Blisters on normal or erythematous skin that rupture easily, leaving large denuded areas.
• Pain: Erosions are extremely painful, contrasting with the intense itching typical of bullous pemphigoid.
• Other mucosal involvement: Erosions can affect the conjunctiva, nasal mucosa, pharynx, larynx, and genitalia.

Physical Examination Signs

• Positive Asboe-Hansen sign: Pressing on an intact blister causes it to extend laterally.
• Positive Nikolsky sign: Gentle lateral pressure on normal-appearing skin induces epidermal shearing and blister formation.
• Extensive raw, weeping, crusted erosions over the trunk, face, and scalp.

• Secondary Bacterial Infection: Sepsis from denuded skin is a leading cause of mortality.
• Dehydration and Malnutrition: Due to severe pain upon eating (oral lesions) and transepidermal fluid loss.
• Iatrogenic complications: Severe side effects from long-term high-dose corticosteroids (diabetes, osteoporosis, avascular necrosis).

Diagnostic Criteria & Guidelines

Diagnosis requires clinical suspicion confirmed by three tests: 1) Histopathology of a lesion showing suprabasal acantholysis, 2) Direct Immunofluorescence (DIF) of perilesional normal skin showing intercellular IgG/C3 deposits in a net-like pattern, and 3) Serology (ELISA) positive for circulating anti-Dsg3 and/or anti-Dsg1 autoantibodies.

Differential Diagnosis

• Bullous Pemphigoid
• Mucous Membrane Pemphigoid
• Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis
• Paraneoplastic Pemphigus

Laboratory Tests & Biomarkers

• Serum ELISA: Positive for anti-Desmoglein 3 and often anti-Desmoglein 1 IgG antibodies. Titers correlate with disease activity.
• Tzanck Smear: Bedside test showing rounded, detached, multinucleated 'acantholytic cells' from the blister base.

Imaging Modalities & Findings

• None:

• Mucosal dominant
  Involvement limited primarily to mucous membranes. Anti-Dsg3 antibodies present; anti-Dsg1 absent.
• Mucocutaneous
  Widespread involvement of both mucosa and skin. Both anti-Dsg3 and anti-Dsg1 antibodies present.

Second-Line & Adjunctive Therapy

For Rituximab failures or contraindications: Immunosuppressants such as Azathioprine (2-3 mg/kg/day PO) or Mycophenolate Mofetil (2 g/day PO). IVIG or Plasmapheresis for severe, rapidly progressive, refractory disease.

Surgical & Procedural Management

Not applicable for primary disease. Meticulous wound care is essential, similar to burn unit management for severe cases.

Recommended Lifestyle Changes

• Eat a soft, bland diet to minimize oral trauma and pain.
• Use a soft-bristled toothbrush and specialized non-irritating mouthwashes (e.g., viscous lidocaine).
• Avoid contact sports or tight clothing that can induce skin shearing.

Patient Counseling & Advice

Warn that healing is slow, and blisters take weeks to resolve. Counsel extensively on the risks of immunosuppression, including the absolute necessity of seeking immediate medical care for fever or signs of infection.

Follow-Up & Monitoring Schedule

Monthly visits during active disease to assess mucosal/skin healing and taper steroids. Monitor anti-Dsg antibody titers via ELISA every 3-6 months to predict clinical relapses. Dexa scan to monitor for steroid-induced osteoporosis.

Preventive Strategies

No primary prevention. Avoidance of known drug triggers in susceptible individuals.

Before steroids, mortality was >90%. Today, mortality is around 5%, mostly due to infectious complications of immunosuppressive therapy. Many patients achieve complete remission off therapy with Rituximab.