Investigations
1st investigations to order
clinical diagnosis
Test
History and characteristic examination findings are often sufficient to diagnose cutaneous lichen planus.
Result
typical clinical features
Investigations to consider
histopathology
Test
Biopsy for histopathology is recommended to establish the diagnosis of lichen planus (LP) in difficult cases. Lesional skin should be selected for biopsy, with punch biopsy being the preferred method. The specimen is fixed in formaldehyde and sent to the laboratory for paraffin fixation and slide generation. Histopathological findings of LP are fairly sensitive and specific. If the expected result is not found, repeat biopsy may be indicated.
At the dermal-epidermal junction, band-like lymphocytic infiltrate and necrotic keratinocytes will be seen. Necrotic keratinocytes will also be seen in the papillary dermis. Sub-epidermal clefts may form and rete ridges may develop saw-toothed patterns. In lichen planopilaris (LP of the scalp), the lichenoid lymphocytic infiltrate involves the adnexal epithelium.[1][2][54]
Result
a band-like lymphocytic infiltrate at the dermo-epidermal junction, necrotic keratinocytes, hyperkeratosis, and hypergranulosis
hepatitis C (HCV) screen
Test
If HCV is suspected, consider serum HCV IgM and IgG tests. These are reported as positive or negative or as a titre.
Serological evidence of HCV may weakly support diagnosis of LP but no diagnostic value is attached to negative results.
If patients have serological evidence of HCV, further work-up (serum liver aminotransferase levels, etc.) and referral to infectious disease specialists may be indicated.
Result
positive or negative
immunofluorescence
Test
Direct immunofluorescence (DIF) testing may be helpful in cases when LP mimics immunobullous disorders and in LP/lupus erythematosus overlap syndrome.
Lesional skin should be selected for biopsy, with punch biopsy being the preferred method. The specimen is fixed in Michel medium or frozen in liquid nitrogen indirectly and sent to the laboratory for slide generation.
Cytoid bodies are present at and below the dermal-epidermal junction with IgM.[52] Shaggy fibrinogen deposition is present at the basement membrane.[1][2][52]
DIF has a sensitivity of 75%, so absence of findings does not exclude the diagnosis.[52]
Result
cytoid bodies with IgM; shaggy fibrinogen deposition
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