Biopsy location key in dermatitis diagnosis.
NEW YORK -- Skin biopsies to confirm dermatitis herpetiformis should be taken from normal-looking skin adjacent to a lesion, and not from within the lesion, Dr. John Zone said at an international symposium on celiac disease. "Twenty percent of skin biopsies from within lesions are negative because the inflammatory infiltrate destroys the antibody," he said.
The hallmark of dermatitis herpetiformis (DH) is granular IgA in the dermal papillae. "On routine histology, this can be confused with some other diseases of the skin, including linear IgA disease and bullous lupus erythematosus, so it really is essential to do direct immunofluorescence to confirm the diagnosis," advised Dr. Zone, professor and chairman of dermatology at the University of Utah, Salt Lake City.
Dermatitis herpetiformis, the skin manifestation of celiac disease, is characterized by intensely pruritic papulovesicles and excoriations on the elbows, knees, buttocks and scalp. It occurs in about 20% of celiac patients, and, like celiac disease, responds to a gluten-free diet. About 10% of first-degree relatives of DH patients will have either DH or another form of celiac disease. "DH does not segregate in celiac families, so one person may have DH and the other may have celiac disease," he explained.
Up to one-third of DH patients will have negative serum antiendomysial antibodies even before starting a gluten-free diet, but such patients will frequently show abnormalities on intestinal biopsy.
"Negative serology does not rule out DH," Dr. Zone stressed, adding that 30%40% of DH patients will have intestinal villous atrophy or villous blunting; 20%-30% will have intestinal intraepithelial lymphocytes; and only 10%-20% will have normal intestinal findings. But in keeping with other manifestations of celiac disease, gastrointestinal symptoms in DH patients do not necessarily correlate with the presence or severity of intestinal abnormalities. Improvement of DH with the elimination of dietary gluten occurs within weeks to months of the initiation of the diet. "In my experience, the time to response correlates with the duration of the disease."
Patients can expect a recurrence of symptoms with the reintroduction of gluten, but this can take place within hours or weeks of ingestion, and the amount of gluten required to produce symptoms varies widely from individual to individual. Treatment with dapsone can suppress the skin inflammation of DH and allow patients to eat gluten without symptoms, but this treatment does not suppress intestinal inflammation.
"DH patients, like other people with celiac [disease], have an increased risk of intestinal lymphoma, which can be reduced with a gluten-free diet," Dr. Zone said. About 10% of DH patients will have a spontaneous remission.
Unlike celiac disease, which is commonly diagnosed in childhood, DH usually presents in patients who are 2030 years old. The mean age of Dr. Zone's patient population is 38 years. "I have ... examined about a thousand DH patients, and I have only seen about 10 kids. It seems that chronic, low-grade, smoldering celiac disease is important in the development of DH."
BY KATE JOHNSON
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|Title Annotation:||Skin Disorders|
|Publication:||Family Practice News|
|Date:||Jan 15, 2007|
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