SHBC1621

K.W.CHEONG¹, S.Y. CHUAH¹, S.I. TEE¹, X.H. ZHAO¹, S. THNG¹

National Skin Centre¹

Diagnosis of lichen planus pigmentosus (LPP) usually requires histological confirmation, but patients with facial involvement are frequently reluctant to undergo skin biopsy. In vivo reflectance confocal microscopy (RCM) is a novel technique which allows the epidermis and the upper dermis to be imaged non-invasively at near-histological resolution. This open observational study aims to correlate the RCM features of LPP with histology, and assess changes in RCM features with response to treatment.

14 patients with a clinical diagnosis of LPP underwent RCM imaging and skin biopsy of the imaged site. Cohen’s kappa (κ) was used to analyse agreement between RCM and histological features, and sensitivity and specificity of RCM to detect histological features were calculated. RCM was repeated at week 9 to assess if RCM markers of disease activity improved with treatment.

There was strong agreement between RCM and histology in detecting spongiosis, epidermal inflammatory cell infiltrate, interface dermatitis, melanophages and dilated blood vessels (κ statistic 0.81, 0.86, 0.59, 1, and 1 respectively), and poor agreement in detecting necrotic keratinocytes and dermal inflammatory cell infiltrate (κ statistic 0.09 and 0.09 respectively).  RCM was sensitive and specific in detecting spongiosis (100% and 91% respectively), epidermal inflammatory cell infiltrate (86% and 100% respectively), and interface dermatitis (100% and 50% respectively). RCM was sensitive in detecting melanophages (100%), and specific in confirming the absence of dilated vessels (100%). Repeat RCM at week 9 demonstrated improvements in markers of disease activity.

RCM is a useful non-invasive tool to diagnose LPP and monitor response to treatment.