A patient with lichen planopilaris (LPP) presents with scarring alopecia. Which immunofluorescence finding on scalp biopsy is characteristic?
- A Linear IgG at the dermoepidermal junction
- B Globular fibrinogen deposits (colloid bodies) in the papillary dermis on DIF ✓
- C Granular IgA at papillary dermis
- D Shaggy fibrinogen at the BMZ with IgM
Correct answer: B. Globular fibrinogen deposits (colloid bodies) in the papillary dermis on DIF
Explanation
In lichen planopilaris, DIF of involved scalp shows cytoid (colloid/Civatte) bodies that stain globularly with IgM, IgG, IgA, and fibrinogen. The most consistent finding is globular deposits of fibrinogen/IgM staining of colloid bodies in the papillary dermis, which represents necrotic basal keratinocytes. There is also shaggy fibrin at the BMZ. This differs from bullous pemphigoid (linear IgG) and DH (granular IgA). Recognizing DIF of LP is important for diagnosis of scarring alopecia.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
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