Subcorneal Pustular Dermatosis Workup

Updated: Feb 11, 2019
  • Author: Lidija Kandolf Sekulovic, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Workup

Approach Considerations

Serum protein electrophoresis

The association of paraproteinemia with subcorneal pustular dermatosis (SPD) is well documented. One study showed 4 of 10 patients with subcorneal pustular dermatosis had a monoclonal gammopathy. Most reported cases have been with IgA monoclonal gammopathies, either kappa or lambda light-chain type. However, immunoglobulin G gammopathies are also reported.

Serum and urine protein electrophoresis should be repeated periodically because the development of paraproteinemia can occur years after the initial eruption of subcutaneous pustular dermatosis. Furthermore, the increased risk of multiple myeloma in patients with a monoclonal gammopathy is well recognized.

Skeletal survey and bone marrow aspiration should be undertaken if multiple myeloma is suspected.

Skin bacterial culture

Subcorneal pustular dermatosis is a sterile eruption. Impetigo and secondary bacterial infections should be excluded.

Skin scraping and fungal culture

Dermatophyte infections need to be excluded. [37]

Skin biopsy

Skin biopsy of an early lesion is needed for histologic analysis and direct immunofluorescence testing.

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Histologic Findings

The classic histologic finding in subcorneal pustular dermatosis (SPD) is subcorneal pustules composed primarily of neutrophils and occasional eosinophils. However, this finding is not specific for subcorneal pustular dermatosis and can be found in other conditions such as pustular psoriasis, acute generalized exanthematous pustulosis, pemphigus foliaceus, bacterial impetigo, and dermatophytosis.

In subcorneal pustular dermatosis, unlike in pustular psoriasis, the epidermis usually has minimal spongiosis. The dermis in subcorneal pustular dermatitis shows a perivascular infiltrate of neutrophils and occasional monocytes and eosinophils. Acantholysis is not prominent; however, it has been reported in older lesions. See the image below.

Subcorneal pustules with neutrophil accumulation a Subcorneal pustules with neutrophil accumulation and minimal spongiosis.

Direct and indirect immunofluorescence studies are typically negative. Nevertheless, periodic repeat studies are recommended to detect epidermal intercellular IgA staining in order to identify a subgroup referred to as subcorneal pustular dermatosis type IgA pemphigus. Desmocollin-1 has been recognized as the autoantigen in this subgroup. [4, 7]

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