What is Dermatitis Herpetiformis?
Dermatitis herpetiformis is a long-term, autoimmune skin condition that causes a severely itchy rash, mainly on the parts of the body that stretch or extend. People often scratch this itchy rash, which can make it hard to see its typical small, fluid-filled blisters. This disease is closely tied to a condition known as gluten-sensitive enteropathy (GSE), which means it’s associated with sensitivity to gluten. Both conditions can trigger the body to produce autoantibodies, or self-attacking proteins, against certain enzymes. In dermatitis herpetiformis, these autoantibodies accumulate in the top layer of the skin. A key part of treating this disease is avoiding gluten and using certain types of medications, such as dapsone.
What Causes Dermatitis Herpetiformis?
Dermatitis herpetiformis can be caused by several factors:
Genetics
Studies have shown that dermatitis herpetiformis is closely linked to certain genes, particularly HLA-DQ2, and somewhat less, HLA-DQ8. Other genes linked to the genetic form of gluten intolerance have also been associated with the condition, including myosin IXB, IL-12, IL-23, and CCR3, although it’s still unclear how they specifically contribute to dermatitis herpetiformis.
Individuals with a blood relative suffering from gluten intolerance or dermatitis herpetiformis have a higher chance of getting one of these conditions. Thus, it might be a good idea for family members to be tested for these conditions. Identical twins share a high risk of both having the disease, with a concordance rate of over 0.9.
Environmental Factors
The leading environmental cause of dermatitis herpetiformis is gluten in food and its component gliadin. Interestingly, a substance known as tissue transglutaminase is responsible for modifying gliadin in the lining of the stomach to a form that triggers an immune response.
Other environmental triggers of dermatitis herpetiformis include exposure to iodine, which can cause flare-ups of the disease, and smoking cigarettes, which is associated with improvement of the skin condition.
Risk Factors and Frequency for Dermatitis Herpetiformis
- Dermatitis herpetiformis is most common in people of northern European descent. Their prevalence ranges from 1.2 to 39.2 per 100,000 people, and incidence rates go from 0.4-2.6 per 100,000 people per year.
- A UK study noted that the number of cases increased from 1990 to 2011, but at the same time, the occurrence of dermatitis herpetiformis fell. Interestingly, those with this condition tend to live longer than expected, probably due to the dietary changes they had to make because of the disease.
- Typically, this condition start affecting people in adulthood, particularly in the fourth decade of life, but it can also occur in children and older adults.
- Men are more likely to have dermatitis herpetiformis than women, with the male-to-female ratio being 1.5-2:1.
- While most common in people of northern European descent, the disease is not common in Asian and African populations. But, it does affect North American populations of European descent similarly to those in northern Europe, implying genetics play a significant role in this disease susceptibility.
- The disease is most often found alongside gluten-sensitive enteropathy (GSE). However, the severity of GSE in individuals with dermatitis herpetiformis can vary widely and can be clinically silent or mild. For this reason, anyone with dermatitis herpetiformis should see a gastroenterologist.
- There’s an increased risk of small bowel lymphoma in patients with dermatitis herpetiformis. Also, the disease is linked to other autoimmune disorders, like autoimmune thyroid disease, so patients should also be screened for this.
- Moreover, patients with dermatitis herpetiformis are at greater risk of having type 1 diabetes, Addison disease, and vitiligo.
Signs and Symptoms of Dermatitis Herpetiformis
People with a skin condition known as dermatitis herpetiformis typically experience itching as a main symptom. They often have a rash that typically appears on the outer parts of elbows, knees, buttocks, and scalp. They might also show symptoms of other associated disorders, one being GSE (Gluten-sensitive enteropathy), which is characterised by bloating, diarrhea, and other digestive discomforts, or symptoms of other autoimmune diseases like hypothyroidism.
This skin condition is identified by reddish, grouped spots and blisters found on the parts of the body that extend or stretch (like elbows and knees). The condition is very itchy, so the blisters are usually scratched open and might look like scratches or scrapes on the skin. Generally, the rashes are symmetrical (appear on both sides of the body in the same places) and do not leave scars as they heal. Patients may even have small purple or red spots on the palms of their hands and soles of their feet. Some people might develop changes in their mouth lining and there have been cases where dental issues, particularly tiny pits on teeth surfaces, are reported. Intriguingly, if a person has GSE, their close relatives may also show these dental defects.
Testing for Dermatitis Herpetiformis
To diagnose dermatitis herpetiformis, doctors rely on the signs and symptoms you’re experiencing, microscopic examination of your skin tissues, specific immune-system tests, and blood tests. A special type of immune test, called direct immunofluorescence, is crucial to this process.
In this test, doctors sometimes take samples from around your skin blisters rather than from the blisters themselves. This is because crucial findings might be lost in the blister tissue. The key finding of this test is the accumulation of a certain immune protein called IgA in specific areas of your skin, appearing in a granular or fiber-like pattern. This band-like pattern is especially common among Asian patients with the skin condition.
Besides IgA deposits, another immune protein, called Complement 3, may also be found in associated with the IgA deposits.
Treatment Options for Dermatitis Herpetiformis
To manage dermatitis herpetiformis in the long term, it’s crucial for patients to strictly follow a gluten-free diet. This approach not only helps improve skin conditions over time, but it’s also important for managing any related gluten-sensitive enteropathy. An experienced dietitian can provide the necessary support for maintaining this diet, as it can be challenging.
Most patients, however, may also need medication in the short to medium term due to the slow results of a gluten-free diet. Dapsone, a type of sulphonamide drug, is very effective in treating dermatitis herpetiformis. It usually eases itching within a few days of beginning the treatment.
Dapsone works by affecting the function and recruitment of neutrophils, which are a type of white blood cell. Prescribed doses typically range from 25 to 150 mg per day. However, this drug can have side effects involving the blood, such as the breaking down of red blood cells, high levels of methemoglobin in the blood, and a low count of white blood cells. Therefore, regular blood tests are necessary, especially at the beginning of treatment. Other side effects may include a severe drug sensitivity reaction and nerve damage. Those with a deficiency of the enzyme glucose-6-phosphate (G6PD) may experience more serious side effects, hence G6PD activity should be checked before starting the treatment. Cimetidine, another drug, can help reduce the side effects of dapsone if given at the same time.
Other sulphonamide drugs such as sulphamethoxypyridazine, sulphapyridine, and sulphasalazine, may also help in treating dermatitis herpetiformis and are often used in patients who cannot tolerate dapsone. Although systemic steroids are not very helpful, powerful topical steroids can temporarily help ease itching.
The main treatments for dermatitis herpetiformis include:
First-line:
* Gluten-free diet
* Dapsone 25 to 150 mg daily
* Potent topical steroids
Second-line:
* Sulphamethoxypyridazine 0.5 to 1.5 g daily (with a gluten-free diet)
Third-line:
* Sulphapyridine 250 to 750 mg daily or
* Sulphasalazine 1 to 2 g daily (with a gluten-free diet)
What else can Dermatitis Herpetiformis be?
When a doctor is trying to diagnose a patient with dermatitis herpetiformis, they have to consider several other skin conditions that have similar symptoms. These could include:
- Linear IgA disease, a rare skin disorder
- Pemphigoid, a group of rare skin conditions
- Eczema, a condition that makes skin red and itchy
- Scabies, a condition caused by tiny mites that burrow into the skin
- Epidermolysis bullosa acquisita, a blistering disease that affects the skin and mucous membranes
Dermatitis herpetiformis often looks quite general or non-specific, so doctors may need to take a small sample of the patient’s skin (a ‘biopsy’) and examine it under a microscope. This can help them find out the true cause of the patient’s itchy skin rashes, particularly if the rashes haven’t improved with treatment.
What to expect with Dermatitis Herpetiformis
Dermatitis herpetiformis is a long-lasting skin condition that requires patients to maintain a lifelong gluten-free diet. Patients who can successfully adhere to this diet and show improvement may have a significantly better long-term outlook and might even be able to lessen or stop their dapsone medication. However, recent studies indicate that patients with this condition who aren’t responsive to a gluten-free diet tend to fare poorly.
Despite its chronic nature, it is possible for the disease to go into remission. This tends to be more common in adults over the age of 40.
Possible Complications When Diagnosed with Dermatitis Herpetiformis
The main issues that can come with dermatitis herpetiformis are tied to GSE (gluten-sensitive enteropathy), which can potentially lead to lymphoma in the small intestine. GSE can make it hard for your body to absorb nutrients, which could result in anemia, weight loss, and osteoporosis. In kids, this could lead to them not growing tall. Dermatitis herpetiformis might also, although not very commonly, be found alongside diseases of the nervous system like ataxia and neuropathy.
Common issues associated with dermatitis herpetiformis and GSE include:
- Increased risk of small bowel lymphoma (a type of cancer)
- Malabsorption (difficulty absorbing nutrients), which can lead to:
- Anemia (not enough healthy red blood cells)
- Weight loss
- Osteoporosis (weak and brittle bones)
- In children, issues with growth resulting in short stature
- Rarely, it can be associated with neurological diseases such as:
- Ataxia (lack of muscle control resulting in shaky movements and unsteady walk)
- Neuropathy (disease or dysfunction of one or more peripheral nerves, typically causing numbness or weakness)