Management

Starting the patient on a strict gluten free diet after making an accurate diagnosis of DH is the only method to ensure resolution of the condition (1)

• gluten free diet includes avoidance of wheat, barley, rye, and their by products. Rice, corn, and oats are allowed
• this diet must be maintained for life since reintroduction of gluten into the diet will cause a relapse of symptoms in a vast majority of patients with DH
• it has the following benefits
  • a sensation of general well-being (of being healthy),
  • resolve both the gastrointestinal and the cutaneous manifestations
  • a reduced need for medication,
  • lower the risk of development of lymphomas and other diseases associated with gluten-induced enteropathy and malabsorption.
• my take several months to years to resolve the cutaneous symptoms if dietary measures are used alone (2)

In addition to gluten free diet, the following can be used for the management of the symptoms

• dapsone
  • is an efficient drug used for symptomatic relief of the rash and will reduce itch substantially within a few days of starting therapy
  • not effective against intestinal symptoms
  • the drug is used
    • as a complementary therapy to a gluten free diet and should be withdrawn slowly once the dietary measure has been established
    • for patients who prefer not to follow a gluten free diet and whom require symptomatic control of the condition (1,2,3)
  • starting dose can be 50 mg/d (to minimize the side effects) which can be increased up to 200 mg/d until the disease is under control
  • a maintenance dose of 0.5–1 mg/kg/d generally will control itching and the development of new skin lesions (2)
  • sides effects of dapsone include:
    • dose dependant
      • haemolysis
        • some degree of haemolysis is inevitable. However those patients with increased risk of glucose-6-dehydrogenase deficiency should be screened before commencing therapy because they can develop acute haemolysis
      • methemoglobinemia
        • may precipitate angina in susceptible patients
    • idiosyncratic
      • hypersensitivity reactions - urticaria, drug rash with eosinophilia and systemic symptoms [DRESS] syndrome
      • agranulocytosis
      • peripheral neuropathy
      • nephropathy/nephrotic syndrome
      • psychosis/anxiety/depression/lethargy (2)
  • monitoring whilst on treatment with dapsone (1)
    • pre-treatment FBC and reticulocyte count - these to repeated weekly for the first four weeks then monthly for 3 months; after initial 3 months then check every 3-6 months
    • other pre-treatment bloods - U+Es, LFTs, g - LFTs and U+Es monitored monthly for first 3 months and then every 3-6 months (2)
• sulfapyridine – for patients who do not tolerate dapsone (specially who develops haemolysis)
• other drugs used for symptom control include:
  • potent (betamethasone valerate or dipropionate) or very potent (clobetasol propionate) topical steroids
  • oral antihistamines
  • other, less effective treatments for dermatitis herpetiformis, include colchicine, prednisolone, ciclosporin and azathioprine - the latter two should be used with caution in patients with dermatitis herpetiformis because of a potential increase in the risk of developing intestinal lymphomas. Phototherapy may provide some symptomatic relief (3,4)

Notes:

• glucose-6-phosphate deficiency (G6PD)
  • patients with G6PD have a two-fold increase in sensitivity towards dapsone-induced haemolytic anaemia People of Mediterranean, African and Asian ancestry are especially at risk and can be tested for this deficiency before dapsone is prescribed
  • for patients unable to tolerate dapsone, particularly those who develop haemolysis, sulfapyridine may be substituted

Reference:

• (1) Jakes AD, Bradley S, Donlevy L.Dermatitis herpetiformis. BMJ. 2014;348:g2557.
• (2) Herrero-González JE. Clinical guidelines for the diagnosis and treatment of dermatitis herpetiformis. Actas Dermosifiliogr. 2010;101(10):820-6.
• (3) Antiga E, Caproni M.The diagnosis and treatment of dermatitis herpetiformis. Clin Cosmet Investig Dermatol. 2015;8:257-65.
• (4) Primary Care Dermatology Society (PCDS). Dermatitis herpetiformis (Accessed 20/03/2017)