Dermatitis Herpetiformis and Linear IgA Bullous Dermatoses Flashcards
(28 cards)
In Dermatitis Herpetiformis, what is the primary autoantigen, and where is it deposited in the skin?
Autoantigen - Tissue Transglutaminase 3 (or epidermal transglutaminase)
What are the DIF findings in Dermatitis Herpetiformis?
Granular IgA deposits
- found in the dermal papillae, particularly at the tips of the rete ridges.
In a patient with dermatitis herpetiformis, what serologic test is most sensitive for gluten sensitivity, and what autoantigen does it detect?
IgA anti - TG2
Target = Tissue transglutaminase 2 (intestinal enzyme)
What histopathologic features are seen on H&E in DH, and how do they evolve across the disease spectrum?
Early = Perivascular neutrohillic inflammation, dermal oedema, +/- Eos
Later = Neutrophilic microabscesses in dermal papillae, subepidermal vesicle or blister, Subepidermal clefting forms from damage at dermal–epidermal junction
What are two key clinical features that distinguish linear IgA bullous dermatosis (LABD) from DH?
Dermatitis Herpetiformis (DH)
* Extensor surfaces: elbows, knees, buttocks, shoulders, posterior neck
* Grouped excoriated papules
* Often with no intact blisters due to intense pruritus and scratching
Linear IgA Bullous Dermatosis (LABD)
* Trunk and limbs, especially lower abdomen, thighs, perioral/periorbital, and groin (may resemble bullous pemphigoid in adults)
* Annular or arcuate plaques
* Peripheral rim of tense vesicles or bullae
What is the key DIF pattern in Linear IgA Bullous Dermatosis, and how does it differ from that seen in bullous pemphigoid?
Linear IgA at the DEJ = LABD
Linear IgG ± C3 at the DEJ = Bullous Pemphigoid
What is the most common drug implicated in drug-induced LABD, and how does its clinical presentation differ from idiopathic LABD?
vancomycin
What drugs can cause LABD?
Vancomycin → #1 cause
Penicillamine
Phenytoin
NSAIDs (e.g., diclofenac, naproxen)
Captopril
Cyclosporine
Beta-lactams (cephalosporins, penicillins)
Biologics (e.g., infliximab — rare)
What is the primary antigenic target in most cases of LABD, and how does this relate to bullous pemphigoid?
BP180, specifically the NC16A domain, just like in bullous pemphigoid (BP).
What is the first-line treatment for DH, and what is its mechanism of action in this disease?
The first-line treatment for Dermatitis Herpetiformis (DH) is dapsone, a sulfone antibiotic with anti-inflammatory properties, particularly targeting neutrophilic inflammation.
- Inhibits neutrophil chemotaxis and adherence to endothelial cells
- Suppresses neutrophil myeloperoxidase activity, decreasing tissue injury
- Rapidly controls pruritus and papulovesicular eruption
- Does not affect underlying gluten sensitivity — that’s addressed by gluten-free diet
What dietary change is curative in DH, and what are two long-term benefits beyond skin improvement?
A strict gluten-free diet is the only curative treatment for Dermatitis Herpetiformis (DH) and the underlying gluten-sensitive enteropathy (celiac disease).
Reduces systemic inflammation
Reduces the risk of gastrointestinal malignancies
** improved nutrient absorption, bone health, and reduced risk of iron, folate, and vitamin D deficiency**
What is the most appropriate first-line treatment for Linear IgA Bullous Dermatosis?
Dapsone
What is the histopathologic difference in the blister cavity between DH and LABD?
A 35-year-old man presents with a 6-month history of intensely pruritic, excoriated papules and erosions on his elbows, knees, and buttocks. He denies blisters, but mentions that he “scratches them off before they rise.” He also reports intermittent bloating and loose stools.
On exam, there are excoriated, crusted papules and erosions on bilateral extensor surfaces. No intact vesicles or bullae are seen. A punch biopsy from an intact lesion shows subepidermal separation with neutrophilic microabscesses in the dermal papillae.
What is the most likely diagnosis?
What is the next best test to confirm it?
Dermatitis Herpetiformis
Next Best Test: Perilesional DIF
And then coeliac serology (TTG2, TTG3, total IgA, Anti-deaminated gliandin peptides)
A 9-year-old girl presents with blistering and crusting lesions on her lower abdomen, inner thighs, and groin. The lesions are grouped vesicles and bullae on a background of erythema, forming annular plaques with peripheral blisters (“string of pearls”). She has no history of celiac disease or GI symptoms. A biopsy shows a subepidermal blister filled with neutrophils and eosinophils.
What is the most likely diagnosis? adn DDx
What treatment is most appropriate as first-line in this patient?
Linear IgA Bullous Disease
DDx: BP
Treatment if Linear IgA = Dapsone
A 60-year-old woman is admitted for MRSA bacteremia and started on vancomycin. After 10 days, she develops pruritic, tense bullae over her trunk, axillae, and groin, many arranged in arcuate clusters. She is afebrile and hemodynamically stable. A biopsy reveals a subepidermal blister with predominant neutrophils and scattered eosinophils. DIF shows linear IgA along the dermal–epidermal junction. Serologies for BP180 and BP230 are negative.
🔍 Question:
What is the most likely etiology of her bullous disease?
What is the first management step?
Linear IgA Bullous Disease
Cause = Vancomycin
Treatment: Cease Vanc, start dapsone
In Dermatitis Herpetiformis, IgA deposits are found in a linear pattern along the basement membrane zone on direct immunofluorescence.
False
Granular pattern, and the tips of the dermal papillae
Dapsone is contraindicated in patients with G6PD deficiency due to the risk of hemolytic anemia.
True
NSAIDS are the most common drug associated with drug-induced Linear IgA Bullous Dermatosis.
False - vancomycin
In children, LABD typically spares the genital and perioral regions.
False
In children, Linear IgA Bullous Dermatosis (LABD) commonly involves the:
Lower abdomen
Groin and genital region
Perioral area
Perineum
Thighs and trunk
Prognosis of LABD?
- Adult: unpredictable course, can remit spontaneously or be chronic
- Childhood: spontaneous remissions frequent, often within 2 years
