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AT-A-GLANCE

AT-A-GLANCE

  • A rare condition with worldwide occurrence.

  • A chronic, recurrent, neutrophilic disorder with a benign course, frequently associated with various forms of immune dysfunction (most commonly immunoglobulin [Ig] A monoclonal gammopathy).

  • Occurrence of intraepidermal deposits of IgA indicates a relationship with IgA pemphigus.

  • Crops of flaccid, coalescing pustules; often in annular or serpiginous patterns.

  • Usually distributed symmetrically in the axillae, groins, submammary, the flexor aspects of the limbs, and on the abdomen.

  • Pathology: subcorneal pustules filled with polymorphonuclear leukocytes.

Subcorneal pustular dermatosis (SPD) is a rare, chronic, recurrent, pustular eruption characterized histopathologically by subcorneal pustules that contain abundant neutrophils. The condition was originally described in 1956 by Sneddon and Wilkinson,1 who separated SPD from other previously unclassified pustular eruptions. Until 1966, when the first comprehensive review appeared, more than 130 cases had been reported, but not all fulfilled the clinical and histopathologic criteria required for this diagnosis.2 A considerable number of additional cases have since appeared in the literature, and a subtype with intraepidermal deposits of immunoglobulin (Ig) A directed against desmocollin 1 has been recognized.3 Today, these cases are usually classified as SPD-type IgA pemphigus, and it is a matter of debate whether the finding of epidermal IgA deposits defines a subset of SPD or a pemphigus variant that is otherwise indistinguishable from “classic” SPD.

EPIDEMIOLOGY

There is no racial predilection. Most of the reported cases have been in whites, but the disease also has been observed in Africans, Japanese, and Chinese. The condition is more common in women and in persons older than 40 years of age, but SPD may occur at any age.2 A pustular eruption that is clinically and histologically similar to the human disease, which also responds to dapsone treatment, has been observed in dogs.4

ETIOLOGY AND PATHOGENESIS

The cause of SPD is unknown. Cultures of the pustules consistently do not reveal bacterial growth. The role of trigger mechanisms such as preceding or concomitant infections, although repeatedly discussed, has remained speculative. Immunologic mechanisms have been implicated in the pathogenesis and in a subset of patients, whose disease clinically resembled SPD, intraepidermal IgA deposits have been detected. Some of these patients also had circulating IgA antibodies against the same sites within the epidermis. Desmocollin 1 and in a single case also desmocollins 2 and 3 have been described as autoantigens in these cases, and the disease has been classified as a pemphigus variant (SPD-type IgA pemphigus; see Chap. 57).3,5-7

The occasional association of SPD with certain other diseases may represent more than a mere coincidence. Increased serum IgA has been detected in a number of patients, and the disease has been reported to occur in cases of IgA-paraproteinemia and IgA multiple myeloma.8-12 In addition, SPD is associated with pyoderma gangrenosum,13,14 ulcerative colitis,15 and Crohn ...

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