Direct immunofluorescence (DIF) of perilesional skin shows IgA deposits in a granular pattern at the dermal papillae tips. The patient has intensely pruritic papules and vesicles on elbows, knees, and buttocks. HLA-DQ2 is positive. Which enzyme is implicated in the autoimmune mechanism of this disease?
- A Transglutaminase 3 (TG3) ✓
- B Transglutaminase 1 (TG1)
- C Desmoglein-1
- D BP180 (type XVII collagen)
Correct answer: A. Transglutaminase 3 (TG3)
Explanation
Dermatitis herpetiformis (DH) shows granular IgA at dermal papilla tips on DIF — a pathognomonic pattern. The autoantigen in DH is epidermal transglutaminase (TG3, also called TGase 3), not the tissue transglutaminase 2 (TG2) targeted in celiac disease serology. Gluten-derived peptides cross-react, leading to IgA anti-TG3 antibody deposition. TG1 is implicated in lamellar ichthyosis. Desmoglein-1 is targeted in pemphigus foliaceus, and BP180 in bullous pemphigoid.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.