MKSAP Quiz: Follow-up for extremely pruritic skin

MKSAP Answer and Critique

The correct answer is B. Dapsone. This content is available to MKSAP 18 subscribers as Question 52 in the Dermatology section. More information about MKSAP is available online.

This patient has dermatitis herpetiformis (DH), and the most appropriate treatment is a gluten-free diet and dapsone. DH is a subepidermal autoimmune bullous disorder that is extremely pruritic. There are small tense vesicles and papules, which are rarely intact, so the usual presentation is excoriations on the elbows, knees, and buttocks. The diagnosis can be confirmed with skin biopsy for routine and direct immunofluorescence testing. Deposition of granular IgA in the dermal papillary tips is pathognomonic of dermatitis herpetiformis. While dapsone is effective in inducing a clinical remission of DH, a gluten-free diet is the preferred long-term therapy. DH has a strong association with celiac disease. Dapsone will successfully treat the skin symptoms of dermatitis herpetiformis, but does not treat the associated gastrointestinal disease. A gluten-free diet treats both the cause and the symptoms of both diseases. In patients with celiac disease, failure to maintain a gluten-free diet increases the risk for small bowel lymphoma. Prior to initiating therapy with dapsone, patients should be checked for glucose-6-phosphate dehydrogenase deficiency because these patients have a high risk of hemolysis on dapsone therapy.

Potent topical glucocorticoids, such as betamethasone valerate, may help alleviate pruritus associated with DH but are not adequate monotherapy and should always be used in combination with dapsone and a gluten-free diet. Long-term side effects of topical glucocorticoids include cutaneous atrophy, striae, and hypopigmentation.

Numerous oral antihistamines are available for the treatment of pruritus, and anecdotal experience suggests that the more sedating antihistamines such as diphenhydramine may have a better antipruritic effect than the less-sedating products. However, DH is not a histamine-mediated disease, and the use of antihistamines for this condition is not very effective and may result in intolerable sedation in some patients.

In addition to the significant complications associated with the long-term use of prednisone, it is not effective in inducing or maintaining clinical remission in patients with DH and should not be used.

For patients who cannot tolerate dapsone, other sulfonamide drugs are a potential treatment option for DH. Case reports suggest that sulfasalazine is effective. While sulfasalazine does not cause hemolysis, there is an increased risk for agranulocytosis and hypersensitivity reactions. As with dapsone, periodic laboratory monitoring for significant side effects is recommended.