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Case Note

Case Note: Pruritic Eruption on the Elbows and Lower Back–Posterior Thigh Region

History

A 35-year-old female with no significant past medical history presents for management of new, intensely pruritic eruption on the elbows, lower back, hips buttocks, and posterior thighs.

Initial evaluation

  • Thin, healthy-appearing young female
  • Family history notable for celiac disease
  • Patient reports vague abdominal complaints, including bloating and intermittent diarrhea
  • Excoriated erythematous papules and plaques with scattered bullae and crusted erosions
  • No evidence of linear burrows or other stigmata of scabetic disease
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Enter your diagnosis

Diagnosis

  • A diagnosis of dermatitis herpetiformis (DH) is rendered
    • Skin biopsies (hematoxylin and eosin stain, direct immunofluorescence) are performed to confirm the diagnosis

Initial Treatment

  • Treatment option discussed
    • Patient opts for treatment to limit progression of new lesions
      • Dapsone 25 mg is prescribed for the first week with a plan to escalate to 100 mg daily dosing
  • Diet review and strict gluten avoidance are recommended, and the patient is referred to nutrition counseling
  • Pre-treatment lab work is ordered
    • Complete blood count with differential
    • Glucose-6-phosphate dehydrogenase levels
    • Thyroid-stimulating hormone and anti-thyroid peroxidase levels are measured based on the patient's report of unexplained weight changes and cold intolerance
  • Patient is referred to gastroenterology clinic for evaluation of celiac disease, malabsorption syndrome, and screening for bowel lymphoma
  • Patient also referred to dental clinic for evaluation of dental enamel defects
  • Follow up in 1 month

Follow-up evaluation strategy

1-month follow-up evaluation:

  • Patient reports that gluten avoidance did not impact her skin lesions or pruritus
  • Skin lesions quickly resolved within a week of initiating dapsone
    • Patient reports that there are far fewer new lesions
  • Subsequent blood work remains normal - indicating that the patient is tolerating the treatment
    • Dapsone dose is escalated to 150 mg daily
  • Follow up in 1 month

Subsequent 1-month follow-up evaluation:

  • Patient reports significant clinical improvement
    • No new lesions
  • Dapsone is continued at 150 mg daily for a further 2 weeks with plan to taper slowly whilst continuing strict gluten avoidance

Further recommendations:

  • Sulfapyridine, supplied in 500 mg tablets, may be used in an initial dose of 1.0-2.0 g per day in patients who cannot tolerate dapsone
    • Taper to the minimum required dose, which is usually 1.0-1.5 g per day
    • If only partial control is obtained on maximal doses of sulfapyridine (4.0 g per day), a small dose of colchicine may be added (0.6 mg once or twice daily)
  • As was recommended in this present Case Note, a gluten-free diet will be effective in most patients
    • DH is gluten dependent
    • Response to gluten avoidance is very slow
      • Clinical response usually requires the patient to be on a rigid gluten-free diet for 6-12 months
    • Although not ideal, even partial gluten avoidance is helpful
    • To obtain dietary directions, the patient should be referred to a dietician skilled in treating patients with celiac disease
    • A successful dietary regimen requires an intelligent, highly motivated patient who dines at home
      • Most patients who adhere to their diet will be able to reduce their medication dose by 50% or more
    • While a gluten-free diet takes 6 months to have efficacy and allow reduction or discontinuation of medication, gluten exposure may be followed by a flare of the skin lesions within hours or days

 Subsequent treatment steps:

  • For dapsone dosing, continue the amount of dapsone for clearing for 2 weeks, then taper the drug by halving the dose every 2 weeks. Maintain the patient on the least amount of dapsone required for control of lesions
    • Although most patients require 50-150 mg daily, some patients are controlled on significantly lower doses (25 mg per week)
    • Once the appropriate dapsone dose is found, complete blood count should be checked on a 6-month basis

General discussion

DH is a chronic, intensely pruritic disorder characterized by symmetrically distributed bullae or erosions, deposition of immunoglobin A (IgA) in the dermal papillae, and evidence of gluten-sensitive enteropathy. Symmetric involvement of bilateral extensor surfaces, scalp, and buttocks, with purpuric lesions on the fingers and toes is the classic presentation. DH is mediated by IgA autoantibodies, like celiac disease, and is a cutaneous manifestation of gluten sensitivity. Components of gluten, particularly gliadin (alcohol-soluble portion of gluten), are converted by transglutaminase into an autoantigen that activates T cell-specific responses with ensuing inflammation and autoantibody production of the IgA class. Whereas patients with celiac disease have predominantly autoantibodies to tissue transglutaminase (tTG), IgA autoantibodies to epidermal transglutaminase (tTG) correlate with DH and are the most sensitive serologic marker of this condition. Production of these antibodies correlates with gluten intake; in some individuals gluten avoidance will result in disappearance of autoantibodies with recurrence upon gluten re-challenge. Only 10% of patients experience spontaneous remission. All patients with DH have gluten intolerance, and many have family histories notable for gluten intolerance and/or autoimmune disease. Specific human leukocyte antigen (HLA) haplotypes, particularly HLA-DQ2 and DQ8, may increase the risk of developing DH. Persons of Northern European descent have the highest prevalence of DH, and there is a male predominance of this condition in the population (approximately 2:1). Typical age of onset is the fourth decade of life. Childhood DH is rare.

DH must be differentiated from other autoimmune blistering diseases, such as bullous pemphigoid, linear IgA dermatosis, pemphigus vulgaris, as well as scabetic or atopic disease. A skin biopsy can be diagnostic, showing neutrophilic collections at the tips of dermal papillae in lesional skin. A direct immunofluorescence will demonstrate granular deposits of IgA at the same dermal location in both perilesional and normal-appearing skin of individuals with DH. Serologic testing for tissue and epidermal transglutaminase may also be diagnostic. ELISA testing for anti-tTG IgA has an estimated specificity of 98-100% and sensitivity of 50-89%. ELISA testing for anti-eTG IgA has an estimated specificity of 93-100% and sensitivity of 60-80%.

The therapeutic strategy is control of pruritus and at least most of the skin lesions through both strict avoidance of gluten and neutrophil-targeted therapy. It is important to note that gluten-avoidance alone is unlikely to result in resolution of skin lesions, whereas rapid response to dapsone is almost universal. Topical or systemic corticosteroids are of little value in DH. In addition, there are other autoimmune conditions associated with DH, most commonly hypothyroidism, as well as an increased risk of non-Hodgkin lymphoma, specifically bowel-associated T cell lymphoma. Dental enamel defects are found in almost half of DH patients, similar to but milder than those described for celiac disease. Patients with DH must be monitored for concomitant disease.

Further reading

Bolotin D, Petronic-Rosic V. Dermatitis herpetiformis, CME: part 1. Epidemiology, pathogenesis, and clinical presentation. JAAD 2011;64:1017-24.

Bolotin D, Petronic-Rosic V. Dermatitis herpetiformis, CME: part 2. Diagnosis, management and prognosis. JAAD 2011;64:1027-33.

Karpati S. Dermatitis herpetiformis. Clinics Derm 2012;30:56-9.

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