Advances in non-invasive techniques as aids to the diagnosis and monitoring of therapeutic response in plaque psoriasis: a review

Plaque psoriasis is a common, chronic, inflammatory disease with a multifactorial etiopathogenesis. Although its diagnosis is often based on clinical features, in ambiguous cases a biopsy with histopathologic confirmation may be necessary. Advanced high-definition imaging techniques may be useful in the study of skin properties in vivo and may facilitate therapeutic monitoring. Available imaging tools vary in their resolution, depth of penetration and visual representation (horizontal, vertical, three-dimensional), and in the type of skin structures visualized. The purpose of this review is to analyze a variety of non-invasive techniques that may assist in establishing definitive diagnoses, as well as in the therapeutic monitoring of psoriasis. These include dermoscopy, videocapillaroscopy (VC), high-frequency ultrasound (HFUS), reflectance confocal microscopy (RCM), laser Doppler imaging (LDI), optical coherence tomography (OCT), optical microangiography (OMAG) and multiphoton tomography (MPT). Their characteristics, indications, advantages, and limits are reviewed and discussed. Dermoscopy may be useful for a first, rapid outpatient evaluation. Videocapillaroscopy and HFUS represent the imaging techniques with the longest history of use in psoriasis. However, whereas VC is useful in both diagnosis and therapeutic monitoring, the utility of HFUS appears to be limited to the monitoring of response to therapy only. Both devices are cost-effective and easy to use in the office setting. Both RCM and OCT allow high-resolution microscopic imaging of psoriatic plaque in a manner comparable with that of virtual histopathology and represent more promising techniques. The utility of LDI, OMAG, and MPT in psoriasis skin imaging requires further study and validation.