Direct immunofluorescence of a lesional skin biopsy in lichen planus characteristically shows:

• A Shaggy deposition of fibrinogen along the basement membrane zone ✓
• B Granular IgA deposits in dermal papillae
• C Intercellular 'fishnet' deposition of IgG throughout the epidermis
• D Linear IgG and C3 along the basement membrane zone

Explanation

Lichen planus shows a shaggy, irregular band of fibrinogen along the basement membrane zone, reflecting chronic interface damage; cytoid bodies may stain with IgM. The fishnet intercellular IgG pattern defines pemphigus vulgaris, linear IgG and A3 at the BMZ defines bullous pemphigoid, and granular IgA in papillae defines dermatitis herpetiformis. Recognising these four DIF patterns reliably separates the blistering and lichenoid disorders.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.