Subcorneal pustular dermatosis masquerading as dermatophytosis

Sir,

Subcorneal pustular dermatosis (SPD) of Sneddon and Wilkinson is a rare disorder presenting with recurrent sterile vesiculopustules affecting predominantly the intertriginous and flexural regions of the body, and rarely the extremities, palms and soles.[1,2] The exact cause of SPD is not yet proven. There is growing evidence that a network of cytokines (TNF-α, IL-18), synthesized by monocytes and keratinocytes might activate neutrophils and induce their migration, thus promoting SPD.[3] Dapsone is the treatment of choice. One case of SPD responded well to colchicine, where dapsone and steroids led to complications.[4] Alternatives include retinoids, phototherapy with psoralen, ultraviolet A (PUVA), and broad or narrow band UVB. The anecdotal use of tacalcitol, ketoconazole, azithromycin, tetracycline, minocycline, vitamin E, cyclosporine, mizoribine, mebhydrolin, infliximab, and adalimumab with mycophenolate mofetil has been reported.[5]

We report a woman with SPD [Figures 1–4] recurring every summer for 30 years. She was treated with systemic and topical antifungals, antibiotics and corticosteroids in the past. The patient responded dramatically to oral dapsone at a dose of 100 mg per day. There was no recurrence for 2 years after treatment with dapsone. The patient is still under follow up. Differentiating SPD from other causes of superficial vesiculopustular eruptions such as miliaria and impetigo can be challenging. However, the classical vesiculo pustule exhibiting the meniscus sign gave away the diagnosis in our case. The repeated use of topical and systemic steroids leading to fungal and bacterial infection perpetuated the disease course in our case. The negative bacterial culture and skin scraping for fungal elements and rapid response to dapsone clearly indicated its non infective nature and the role of neutrophils in the pathogenesis of the disease.

Figure 1.

Papules and pustules scaling mimicking tinea incognito over the axilla

Figure 4.

Histology under high power showing subcorneal cleft containing neutrophils

Figure 2.

Vesiculo pustule exhibiting the meniscus sign over the chest

Figure 3.

Histology under low power showing subcorneal cleft containing neutrophils with moderate inflammatory infiltrate in the dermis

In elderly females with recurrent pustular eruptions mimicking dermatophytosis, SPD should be considered as a possibility. As there is likelihood of immune dysregulation in patients with SPD, it is mandatory that every patient diagnosed as SPD is followed up for the development of any of the abovementioned or other diseases.