Correspondence Address:
Dr. Yun- Ting Chang
Department of Dermatology, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Road, Taipei
Taiwan

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Dear Editor,

Immunoglobulin (Ig) A pemphigus is a rare type of autoimmune bullous dermatosis characterized by intercellular deposits of IgA in the epidermis.[1],[2] IgA pemphigus can be primarily classified into subcorneal pustular dermatosis (SPD) and intraepidermal neutrophilic (IEN) dermatosis.[3] Herein, we report a HLA-B*13:01-positive case of IEN-type IgA pemphigus successfully treated with oral corticosteroids.

A 63-year-old male presented with a 1-week history of a blistering eruption. The eruption started as pruritic papules, vesicles, and pustules on the chest and buttocks. The lesions gradually increased in number and appeared on the face, scalp, axillae, back, inguinal folds, and proximal extremities. Many lesions expanded peripherally to form oval or round plaques with central crusting and peripheral beading of pustules [Figure 1]. The patient had dyslipidemia and was started on regular use of rosuvastatin 1 month before the development of eruption. He had no known food or drug allergies.{Figure 1}

Histologically, there were intraepidermal clefts filled with a dominant number of neutrophils, along with a few lymphocytes and eosinophils [Figure 2]. Some acantholytic keratinocytes were also present. There was moderate perivascular lymphohistiocytic and neutrophilic infiltration in the upper dermis. No pathogens were identified by Gram stain, periodic acid-Schiff stain, or acid-fast stain. Direct immunofluorescence microscopy demonstrated intercellular deposition of IgA autoantibodies throughout the whole layer of the epidermis. There was no deposition of C3, IgG, and IgM in the epidermis. The workup for monoclonal gammopathy showed a normal serum level of IgA antibodies. Results of serum electrophoresis were unremarkable.[4]{Figure 2}

We intended to treat the patient with dapsone. Therefore, the patient was examined for the glucose-6-phosphate dehydrogenase (G6PD) level, and the allele HLA-B*13:01 was determined. The results showed no G6PD deficiency but the presence of the allele HLA-B*13:01.[5],[6] To avoid the occurrence of severe cutaneous adverse reactions, we treated the patient with oral prednisolone. The initial dose of prednisolone was 1 mg/kg/day. The pustules gradually crusted, without the development of new lesions after initiating the therapy. Two weeks later, the patient was discharged with a tapering course of prednisolone. He has been regularly followed up at our clinic for 2 years, and there are no signs of recurrence. Rosuvastatin was continued during the follow-up period, and drug-induced pemphigus was excluded.

The most commonly encountered subtypes of IgA pemphigus are SPD and IEN. Histologically, the SPD type is characterized by the presence of subcorneal neutrophilic pustules, whereas the IEN type is characterized by neutrophilic abscesses distributed in any layer of the epidermis. In the immunofluorescence study, the SPD type is characterized by intercellular deposition of IgA autoantibodies in the upper epidermis, whereas the IEN type is characterized by intercellular deposition of IgA autoantibodies in the lower or entire epidermis.

Dapsone is effective in inhibiting neutrophilic chemotaxis and is regarded as a first-line treatment for IgA pemphigus.[7],[8] However, dapsone should be used with caution owing to its common pharmacologic and idiosyncratic adverse effects in vulnerable individuals. Evidence has indicated a strong association between HLA-B*13:01 and dapsone-induced severe cutaneous adverse reactions.[5],[6],[9] The prevalence of HLA-B*13:01 varies across races, with the highest prevalence among Chinese population, which is up to 15%–20%.[6] Therefore, routine screening of HLA-B*13:01 may be necessary for Chinese people before the dapsone therapy. HLA-B*13:01-positive patients with IgA pemphigus should be alternatively treated with corticosteroids or other less frequently used immunosuppressants.[1]

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