IgA pemphigus

What is IgA pemphigus?

IgA pemphigus (or immunoglobulin A pemphigus) is an autoimmune blistering disorder. It is also called intercellular IgA dermatosis among other names.

IgA pemphigus has two major subtypes:

• Subcorneal pustular dermatosis (SPD) type
• Intraepidermal neutrophilic (IEN) type.

However, a new classification describes five subtypes of IgA pemphigus; these being:

• SPD type IgA pemphigus
• IEN type IgA pemphigus
• IgA-pemphigus vegetans
• IgA-pemphigus vulgaris
• Unclassified IgA pemphigus.

Who gets IgA pemphigus?

IgA pemphigus is very rare. It most commonly affects the middle-aged and old people, but it can affect people at any age, with a case reported in a 1-month-old child.

What are the clinical features of IgA pemphigus?

The clinical features of IgA pemphigus include blisters, pustules, erythema, erosions and vegetating lesions.

• The first signs are flaccid vesicles and pustules.
• The vesicles and pustules rupture to form erosions and crusted plaques.
• The eruption tends to follow an annular pattern.

IgA pemphigus appears to favour the trunk, upper and lower extremities, axillae, and groin. Mucosal involvement is infrequent.

What is the cause of IgA pemphigus?

The exact cause of IgA pemphigus is unclear.

• IgA autoantibodies bind to desmogleins or desmocollins, the cells responsible for adhesion between cells.
• In SPD-type IgA pemphigus, the autoantigen is described as desmocollin 1, one of the desmosomal cadherins, the glycoproteins that maintain the shape of a cell.
• In at least some cases of IEN-type IgA pemphigus, the autoantigens are desmoglein 1, desmoglein 3, and an unspecified transmembrane protein.

What is the differential diagnosis for IgA pemphigus?

Other conditions that should be considered in the differential diagnosis include:

• Bacterial skin infection
• Dermatitis herpetiformis
• Pemphigus foliaceus
• Eosinophilic pustular folliculitis
• Subcorneal pustular dermatosis.

How is IgA pemphigus diagnosed?

A blistering autoimmune disease or autoinflammatory pustular disease may be suspected clinically from the clinical features, often after the eruption has failed to clear with antibiotics.

The diagnosis of IgA pemphigus requires a skin biopsy for histology and direct immunofluorescent testing.

• In IgA pemphigus, a skin biopsy reveals an intraepidermal blister. There is a mixed dermal inflammatory infiltrate, with intraepidermal neutrophil infiltration.
• Direct immunofluorescence of a skin biopsy of healthy appearing skin close to the area of blistering reveals IgA deposition in epidermal keratinocyte cell membranes.

Indirect immunofluorescence testing of serum can show IgA anti-keratinocyte cell-surface antibodies. Immunoglobulin G (IgG) anti-keratinocyte cell-surface antibodies have also been reported.

What is the treatment for IgA pemphigus?

The main medications used to treat IgA pemphigus are systemic steroids and dapsone.

Since few cases of IgA pemphigus have been described, the most effective treatment is unknown. Other medications worth considering include:

• Colchicine
• Mycophenolate mofetil
• Isotretinoin
• Acitretin
• Adalimumab.