Recurrent Amicrobial Pustulosis Responded Well to Dapsone

Sir,

Amicrobial pustulosis (AMP) of the folds is a rare cutaneous disease characterized by relapsing sterile pustules frequently associated with autoimmune disorders.

A 60-year-old male, a known diabetic, presented with a 2-year history of recurrent pus-filled lesions in the axilla, trunk, and groin without any constitutional symptoms. On examination, multiple discrete pustules were found on an erythematous base over the axilla, cubital fossa, groin, and sides of trunk with sparing of involvement of the scalp, palms, soles, nails, and mucosa [Figure 1]. A clinical diagnosis of pustular psoriasis was first considered. The patient received acitretin 25 mg twice daily for 2-3 months and showed minimal improvement. He developed recurrence and flare of pustular lesions. Gram stains showed polymorphs and were negative for microorganism. Pus culture was sterile. Skin biopsy showed basket weave orthokeratosis, mild spongiosis, mild hypogranulosis, and focal basal cell vacuolization. Dermis showed moderately dense interstitial mixed inflammatory infiltrate including few neutrophils and lymphocytes. He was put on antibiotics and colchicin. Later, colchicin was stopped due to gastrointestinal intolerance. Methotrexate was started and in spite of receiving its increased dose, the patient continued to develop new pustules. Repeat biopsy showed basket weave stratum corneum with focal parakeratosis, moderate acanthosis with focal neutrophilic exocytosis, and a large spongiform pustule in stratum spinosum with mixed inflammatory infiltrate in superficial dermis [Figure 2]. Direct immunofluorescence was negative. All routine biochemical investigations were normal. His autoimmune profiles were negative and rheumatoid factor was positive, although anti-cyclic citrullinated peptide was negative. After repeat biopsy, sterile culture, negative stains, and failure to respond to treatment, a working diagnosis of AMP of folds was made. Methotrexate was stopped. Dapsone was started at a dose of 100 mg daily. The patient showed significant improvement 2 weeks after dapsone therapy. He had no pustular lesions; erythema and scaling were resolved, leaving behind hyperpigmentation, 4 weeks after dapsone therapy [Figure 3]. Dapsone was gradually tapered and stopped after 10 weeks. AMP is a recurrent, aseptic pyoderma involving mainly the skin folds such as the external acoustic meatus, scalp, pubis, and digits and is often associated with autoimmune diseases or immunological abnormalities.[1] Diagnosis of the condition is challenging and is based on histologic correlation, negative tissue stains, and negative microbiological culture. Associated autoimmune conditions are undifferentiated connective tissue disease, systemic lupus erythematosus, antiphospholipid syndrome, Crohn's disease, Hashimoto thyroiditis, myasthenia gravis, Sjogren syndrome, celiac disease, rheumatoid arthritis, idiopathic thrombocytopenic purpura, and immunoglobulin A nephropathy.[2] According to Marzano et al.,[3] the diagnostic criteria of AMP include obligate criteria of pustulosis affecting one or more major folds, histologic findings of intraepidermal spongiform pustulosis with neutrophil infiltrate in the dermis, and aseptic pustules and the minor criteria include association with one or more autoimmune disorders, positive antinuclear antibody (ANA) titers of 1:160 or more, and the presence of additional autoantibodies.[3] Differential diagnoses of sterile pustulosis include diseases such as Sneddon–Wilkinson disease, acute generalized exanthematous pustulosis, pemphigus vegetans, pustular psoriasis, and immunoglobulin A pemphigus. So, the diagnosis is based on clinicopathologic correlation after excluding the infectious causes of subcorneal pustulosis, candidiasis, folliculitis, and impetigo.[2,4] AMP predominantly affects young females.[3] There is no standardized treatment for AMP. The most effective treatment reported is oral and systemic corticosteroid.[3] Other therapeutic modalities with chloroquine, dapsone,[5] cyclosporine,[5] colchicines, cimetidine, and zinc have been used. There is an isolated report of a combination of cimetidine and ascorbic acid inducing clinical remission.[3] Recently, the efficacy of interleukin 1 (IL-1) receptor antagonist anakinra has been reported in two cases[6] and also of an anti-TNF-alpha drug and an anti-IL-12/23 agent (infliximab and ustekinumab).[7]

Figure 1.

Multiple discrete pustular lesions on an erythematous base present over the trunk

Figure 2.

Spongiform pustule in stratum spinosum with moderate acanthosis and spongiosis in underlying epidermis basket weave stratum corneum with focal parakeratosis at the edges (H&E, ×100)

Figure 3.

Resolved pustular lesions with postinflammatory hyperpigmentation

In our case, oral retinoids, methotrexate, and colchicin failed to control the eruption, and oral antibiotics resulted in transient improvement. Dapsone gave significant improvement. The dose was reduced gradually and stopped completely; since then, there was no relapse.

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Conflicts of interest

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