Differential diagnosis

The main differential diagnosis of the disease includes pemphigus foliaceous, pustular psoriasis, acute generalized exanthematous pustulosis, dermatitis herpetiformis, necrolytic migratory erythema, bacterial impetigo, dermaphytosis, and subcorneal postural dermatosis.

Diagnosis

Subcorneal pustular dermatosis (SPD). Also known as Sneddon and Wilkinson dermatosis.

Biopsy of the removed skin lesion revealed subcorneal pustules, with a neutrophilic infiltrate and minimal spongiosis. The pathologist reported that the picture was very suggestive of a pustular dermatopathy, strongly resempling subcorneal pustular dermatosis. In addition, cultures were negative.

Diagnosis in our patient was, partially, made by exclusion of other diseases with similar manifestations. Specifically, his negative past medical history, his afebrile, non-systematic, clinical course, the gross morphology and the localization of the skin lesions were against pustular psoriasis, necrolytic migratory erythema, acute exanthematous pustulosis, and dermatitis herpetiformis. In addition, histology findings were against pemphigus foliaceous, pustular psoriasis, acute exanthematous pustulosis, and dermatitis herpetiformis. Finally, the repeated sterile cultures from specimens of lesions were against bacterial impetigo and dermatophytosis.

Therapy

Treatment with dapsone -the drug of choice for this condition- was considered. However, his skin condition improved dramatically within the first week after his first biopsy, while we were planning for a second biopsy. At that period the patient was receiving treatment with azithromycin 250 mg per day by month (for a total of 7 days) for the management of possible non-specific urethritis. In addition, he also received local treatment with steroid plus keratolytic agent (flumetasone pivalate 0.02% + salicylic acid 3%) twice daily, as an empiric regimen.

Useful remarks

• Subcorneal pustular dermatosis (SPD) is a rare, chronic, relapsing, pustular dermatosis that usually develops in women over 40 years of age. Eruption is variably pruritic. Characteristically, the lesions spare the mucous membranes and the face. In the contrary, there is a predilection for the axillae, inguinal and mammary folds, as well as for the flexor surfaces.
• IgA monoclonal gammopathy, IgA multiple myeloma and, less oftern, IgG multiple myeloma have all been reported to be related to SPD 1,2.
• Therapy of SPD is not uniformly successful. Dapsone, 50-100 mg per os once a day long periods, is considered to be the most effective therapy. Other commonly used regimens include colchicine, retinoids, corticosteroids (both systematic and potent local), ketoconazole, sulfapyridine and sulfamethoxypyridazine, all with different rates of success2.

Reference list

1. Atukorala DN, Joshi RK, Abanmi A, et al. Subcorneal pustular dermatosis and IgA myeloma. Dermatology 1993;187:124-6.
2. Reed J, Wilkinson J. Subcorneal pustular dermatosis. Clinical Dermatology 2000;18:301-13.

Acknowledgements

1. This case was prepared for our website by I. Bliziotis, MD.
2. A full version of this case and a review of the relevant literature were accepted for publication in the Journal of Infection [Bliziotis I, Rafailidis P, Vergidis P, Falagas ME. Regression of subcorneal pustular dermatosis lesions with azithromycin. Journal of Infection, 2004 (in print)].