Treatment of Dermatitis Herpetiformis
Dapsone, a sulfone, was synthesized in the early twentieth century and has held longtime FDA approval to treat dermatitis herpetiformis and leprosy. However, unlabeled uses of dapsone have become prevalent among dermatologist, especially in autoimmune bullous diseases (AIBD). Dapsone is a lipid-soluble drug that penetrates well into various tissues. It comes as 25 and 100 mg tablets, being the dosage between 25 and 300 mg daily. It is known to inhibit neutrophil chemotaxis. It is metabolized in the liver by acetylation and hydroxylation, having a half-life elimination of 30 h, which allows daily dosing. The serum levels of dapsone can be increased by TMP-SMX, folic acid antagonists, and probenecid. Pharmacologic side effects include methemoglobinemia and hemolytic anemia; monitoring patients for signs of jaundice and hemolysis is recommended. Idiosyncratic side effects are several and include agranulocytosis, gastrointestinal irritation, peripheral neuropathy, psychosis, dapsone hypersensitivity syndrome, and cutaneous hypersensitivity reactions. Relative contraindications include renal and liver dysfunction. Dapsone is considered pregnancy category C. Initial monitoring includes glucose-6-phosphate dehydrogenase (G6PD) complete blood count, and liver function test. Subsequent blood work should be weekly for the first month while titrating up the medication, then monthly for 3 months, and finally every 3 months. The aim of this chapter is to review the use of dapsone in the management of AIBD such as dermatitis herpetiformis, pemphigus, pemphigoid, bullous systemic lupus erythematosus, epidermolysis bullosa acquisita, linear IgA bullous dermatosis, and IgA pemphigus.
