Reflectance confocal microscopy for the characterization of primary cutaneous amyloidosis: a pilot study

PRIMARY CUTANEOUS amyloidosis (PCA) is a pruritic and potentially disfiguring disorder, this disease may impact greatly on a patient’s social and emotional status. The most common subtypes are macular amyloidosis (MA) and lichen amyloidosus (LA), or a mixed subtype of the two (biphasic amyloidosis) (1). PCA is usually diagnosed clinically due to its common occurrence. However, for cases with atypical presentations or for those physicians not familiar with PCA, the diagnosis can be a challenge and skin biopsy may be necessary to confirm the presence of amyloid in dermal papillae. In vivo reflectance confocal microscopy (RCM) is a new tool. The ability to evaluate a skin lesion microscopically in a non-invasive and real-time fashion has long been a goal for dermatologists and dermatopathologists (2, 3). This study was designed to study the diagnostic applicability of RCM for PCA. In this study, we present characteristic RCM features of 20 patients with PCA and demonstrate the value of RCM in the diagnosis of PCA. Participants were enrolled from The Third People’s hospital of Hang Zhou from May 2015 to September 2015. Informed consent was obtained. Previous history of Er:YAG or carbon dioxide laser dermabrasion to treat PCA was the only exclusion criteria. Only patients with typical clinical presentations of PCA, either macular or lichen subtypes, were included in this study. A commercially available in vivo RCM device (Vivascope 1500; Lucid Inc., Rochester, NY, USA) was used for imaging. The instrument operates with a diode laser at an 830 nm wavelength and a laser power <35 mW at tissue level. This system provides high-resolution images (approximately 1–2 lm in the lateral dimension and 4–5 lm in the axial ones) to a depth of 200–350 lm in vivo (from the epidermis down to the superficial reticular dermis). Histopathology findings: A total of 20 clinically diagnosed PCA patients were enrolled. Eleven patients had lesions consistent with MA, and nine with LA. All patients underwent skin biopsy and their histopathological findings were compatible with PCA, including basal hyper pigmentation, pigment incontinence, and amyloid deposition in the papillary dermis (Figs 1c and 2c). In addition, compact orthohyperkeratosis and acanthosis were also found for most LA specimens. Reflectance confocal microscopy features: Hyperkeratosis and acanthosis in the epidermis, dermal papilla present cloud-like agglomerate which are high refractive index (n = 20). There were some dotted substance, coliform substance, rope and so on in the agglomerate. The annular structure of papillary dermis increases and appear pleomorphism (Fig. 1b). In addition, the increased melanin in the basal cell layer was also observed (Fig. 1a). At the level of the dermal-epidermal junction, papillary rims, which usually are visible in normal skin, are obscured, total or partial obliteration of the ring-like structures around the dermal papillae. Melanophages, visible as brightly refractile, plump, oval to stellateshaped cells, infiltrate in the layer of dermis, associated with a few scattered round-to-polygonal, mildly refractive cells (Fig. 2a and b). Most clinical lesions of PCA showed brownish color, its diagnosis is usually straight