Dermatitis herpetiformis is a chronic, pruritic, autoimmune, blistering skin condition. It is the cutaneous manifestation of coeliac disease. It presents as clusters of small vesicles or papules on the extensor surfaces (elbows, knees, and buttocks).
It peaks at 30 – 40 years and is more common in men.
- Risk factors
- HLA D12 and HLA DQ8
- Exposure to gluten
- Coeliac disease (80% have varying degrees of gluten-sensitive enteropathy)
- Male sex
- Pathophysiology
- Gliadin peptides are indigestible in genetically susceptible individuals
- They cross the intestinal epithelium and interact with tissue transglutaminase, forming deamidated gliadin-tTG complexes
- Anti-tTG IgA antibodies are formed against these complexes. The tantibdies cross-react with epidermal transglutaminase (eTG) found in the dermal papillae
- Deposition of IgA-eTG immune complexes in the dermal papillae causes inflammation → subepidermal blister formation (manifesting as vesicles and bullae)
- Mast cells release histamine, causing intense pruritus
- Signs and symptoms
- Symmetrical, erithematous and intensely pruritic papules and vesicles
- Distributed over extensor surfaces (elbows, knees, and buttocks)
- Excoriation and crusting due to scratching
- Symmetrical, erithematous and intensely pruritic papules and vesicles
- Differentials
- Bullous pemphigid
- Linear IgA disease
- Investigations
- Skin biopsy: granular IgA deposits in the dermal papillae
- Serology to detect IgA anti-tTG antibodies and IgA anti-endomysial antibodies
- Upper gastrointestinal endoscopy with small bowel biopsy: for villous atrophy and crypt hyperplasia
- Treatment
- Gluten-free diet
- Dapsone to relieve pruritus
- Sulfapyridine and colchicine in patients who cannot tolerate dapsone
- Complications
- Enteropathy-associated T-cell lymphoma
- Small bowel adenocarcinoma
- Osteoporosis
- Malabsorption syndromes
- Hypothyroidism
- Secondary bacterial infection
- Lichenification and hyperpigmentation due to persistent pruritus and scarring
