Linear IgA Dermatosis

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Overview

Linear IgA dermatosis is a bullous disorder that resembles dermatitis herpetiformis or bullous pemphigoid but is distinguished from these disorders by the linear deposition of IgA at the epidermodermal junction and the absence of gluten-sensitive enteropathy. Many cases are drug-induced, and culprit drugs include vancomycin, lithium, amiodarone, carbamazepine, captopril, penicillin, PUVA, furosemide, oxpprozin, IL-2, interferon-gamma, phenytoin, diclofenac, statins, tea tree oil, angiotensin receptor antagonists, and glibenclamide. The therapeutic strategy is relief of symptoms and control of blister formation.

First Steps

1. For drug induced disease, discontinue the culprit drug.
2. For idiopathic disease, treat with dapsone as described below:

A. Linear IgA dermatosis is initially treated with oral dapsone 100 mg/day. Expect a clinical response within 5-10 days.
B. If blistering is not controlled, increase dapsone every 1-2 weeks in 25-mg increments until the desired clinical response is obtained. Most patients will require 300 mg or less. Check CBC weekly or every 2 weeks as dapsone is increased.
C. Colchicine may be used to supplement the dapsone dose, beginning at 0.6 mg once or twice daily, maximum dose 1.2 mg twice daily.

Subsequent Steps

Taper dapsone by 50-mg increments every 2 weeks until the appropriate maintenance dose is achieved. The maintenance dose should be the level at which the patient gets an occasional blister. Continue therapy indefinitely.

Alternative Steps

1. Sulfapyridine offers an alternative for dapsone-allergic individuals or for patients who do not tolerate its side effects of nausea, lethargy, and depression. Use an initial dose of 500 mg twice daily and increase dose by 1 gram every 1-2 weeks until the disease is controlled. Control may require 1-4 gm/day.
2. If partial control is attained with maximal doses of sulfapyridine (4 gm/day), benefit may be derived by adding small amounts of dapsone (25-50 mg/day).
3. Mycophenolate mofetil 2-3 grams daily can be used for refractory cases.
4. An occasional patient will respond to an oral antibiotic, erythromycin, or a tetracycline.
5. Intravenous immunoglobin (IVIG) has led to partial responses in very refractory cases.

Pitfalls

1. Patients should be screened for G6PD deficiency, as dapsone causes acute hemolysis in these individuals.
2. Monitor hemoglobin and hematocrit, as dapsone causes dose-related hemolysis and methemoglobinemia.
3. Although a rare complication, dapsone causes hepatitis and renal toxicity.
4. If the patient does not respond to dapsone or sulfapyridine, the diagnosis should be reevaluated, especially for a drug causing the eruption.

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