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Pruritic blistering rash

A 71-year-old man presented to the family medicine skin care clinic with a painful, pruritic, blistering rash of 3 months’ duration that had spread diffusely over his body, including his trunk, extensor extremities, and face. He said that the blisters had been rupturing spontaneously. He denied any blistering in his mouth. He had not taken any antibiotics recently; his medications included duloxetine, terbinafine, and gabapentin.

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References

This patient was given a diagnosis of linear IgA bullous dermatosis (LABD) based on biopsy results. (Biopsy is extremely helpful in differentiating bullous disorders.) A shave biopsy of 1 of the mid-chest 3-mm vesicles and a perilesional punch biopsy sent in Michel media showed linear deposition of IgA and IgG along the basement membrane zone and subepidermal blister with neutrophils and eosinophils. The IgA appeared stronger in the direct immunofluorescence study and there were numerous neutrophils on histology, which confirmed the diagnosis.

LABD is one of the less common blistering disorders. It has a bimodal distribution occurring mostly in adults around 60 years of age and a lower peak incidence in young children.1 It often manifests with an acute onset of tense vesicles and bullae. The lesions can be extremely pruritic and can appear on mucous membranes, normal skin, or inflamed skin. Lesion formation is often sudden and manifests in clusters with an erythematous base on the trunk, extensor extremities, buttocks, and face—especially the area in and around the mouth.1

LABD is diagnosed by linear deposits of IgA at the dermo-epidermal interface by direct immunofluorescence. The mechanism for lesion formation is still not well known. It can occur spontaneously or can be drug-induced. In many individuals with LABD (such as this one), the precipitating event for the disease is unknown.

It is important to differentiate LABD from other blistering diseases that can also affect the oral mucosa. Bullous pemphigoid has tense vesicles, as well, but often has a prodromal phase before lesions appear in a nonclustered pattern on the skin.2 Pemphigus vulgaris, which is also in the differential, is characterized by soft blisters and almost always includes the oral mucosa, which is usually where lesions first develop.

Dapsone is first-line therapy. However, due to the risk of hemolysis with dapsone treatment in patients with glucose-6-phosphate dehydrogenase (G6DP) deficiency, the physician confirmed that the patient had normal levels of G6DP before starting the patient on dapsone 25 mg/d po. After starting dapsone, the patient reported unexplained syncopal episodes and falls and stopped the medication. (This was not an anticipated adverse effect.) The patient was then started on colchicine 0.6 mg orally tid. (Other second-line therapies include sulfapyridine and sulfamethoxypyridazine.1) Follow-up in 1 month was scheduled.

Image courtesy Daniel Stulberg, MD. Text courtesy of Riley Diehl, MD, Department of Internal Medicine, and Daniel Stulberg, MD, FAAFP, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque. Photo courtesy Daniel Stulberg, MD.

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