Dermatitis Herpetiformis (DH)

Dermatitis Herpetiformis is a chronic, intensely pruritic, papulovesicular eruption that represents the cutaneous manifestation of gluten sensitivity. It has a strong association with celiac disease and shares similar immunologic pathways.

Key Points:

• Affects 10-39 per 100,000 individuals
• Peak onset in pediatric population: 2-7 years
• Male:Female ratio = 2:1
• Strong genetic predisposition (HLA-DQ2 and HLA-DQ8)
• 100% association with gluten sensitivity

Immunological Mechanism

• Type IV hypersensitivity reaction
• IgA autoantibodies against tissue transglutaminase (tTG)
• Epidermal transglutaminase (eTG) is the primary autoantigen
• Formation of immune complexes in dermal papillae

Genetic Factors

• HLA associations:
  • HLA-DQ2 (90% of cases)
  • HLA-DQ8 (remaining cases)
• Family history of celiac disease or DH increases risk
• Autoimmune disease associations

Inflammatory Cascade

• Gluten exposure triggers immune response
• IgA deposition in dermal papillae
• Neutrophil recruitment and activation
• Release of inflammatory mediators
• Formation of subepidermal vesicles

Cutaneous Manifestations

• Primary Lesions:
  • Symmetrical, grouped excoriated papules
  • Vesicles with herpetiform arrangement
  • Urticarial plaques
  • Erosions and crusts from scratching
• Distribution Pattern:
  • Extensor surfaces: elbows, knees
  • Buttocks and sacral region
  • Scalp and posterior neck
  • Upper back and shoulders

Associated Symptoms

• Intense pruritus (cardinal symptom)
• Burning sensation
• Pain at lesion sites
• Chronic sleep disturbance due to itching

Gastrointestinal Features

• Often asymptomatic despite enteropathy
• Possible symptoms:
  • Abdominal pain
  • Diarrhea
  • Malabsorption
  • Growth failure

Diagnostic Approach

• Clinical History:
  • Characteristic distribution
  • Intense pruritus
  • Response to gluten exposure
  • Family history
• Skin Biopsy:
  • Histopathology: neutrophilic microabscesses in dermal papillae
  • Direct immunofluorescence (gold standard):
    • Granular IgA deposits in dermal papillae
    • Perilesional skin biopsy required

Laboratory Studies

• Serologic Testing:
  • Anti-tissue transglutaminase (tTG) IgA
  • Anti-endomysial antibodies (EMA)
  • Anti-epidermal transglutaminase antibodies
  • Total serum IgA level
• HLA typing (if diagnosis unclear)
• Small bowel biopsy (not routinely required)

Differential Diagnosis

• Linear IgA bullous dermatosis
• Bullous pemphigoid
• Scabies
• Atopic dermatitis
• Papular urticaria
• Contact dermatitis

Pharmacological Treatment

• First-Line:
  • Dapsone:
    • Starting dose: 0.5-1.0 mg/kg/day
    • Maintenance: 50-150 mg/day
    • Rapid relief of symptoms (24-48 hours)
• Alternative Medications:
  • Sulfasalazine
  • Sulfamethoxypyridazine
  • Topical corticosteroids (symptomatic relief)

Monitoring

• Pre-Dapsone Screening:
  • G6PD deficiency
  • Complete blood count
  • Liver function tests
  • Renal function
• Follow-up:
  • Weekly CBC for first month
  • Monthly monitoring thereafter
  • Regular liver and renal function tests

Dietary Management

• Strict Gluten-Free Diet (GFD):
  • Cornerstone of long-term management
  • Takes 6-24 months for full effect
  • Allows reduction/discontinuation of medications
  • Prevents complications
• Dietary Counseling:
  • Registered dietitian involvement
  • Education about hidden sources of gluten
  • Nutritional supplementation if needed
  • Family education and support

Potential Complications

• Medication-Related:
  • Dapsone side effects:
    • Hemolysis
    • Methemoglobinemia
    • Agranulocytosis
    • Peripheral neuropathy
• Disease-Related:
  • Growth failure
  • Malabsorption complications
  • Increased risk of lymphoma
  • Associated autoimmune conditions

Long-term Outcomes

• Favorable with strict GFD adherence
• Possibility of medication discontinuation
• Risk of relapse with gluten exposure
• Need for lifelong dietary compliance

Follow-up Care

• Regular dermatology visits
• Monitoring of associated conditions
• Annual screening for complications
• Dietary compliance assessment
• Quality of life evaluation