Dermoscopic Features of Primary Cutaneous Amyloidosis

Abstract and Introduction

Abstract

Background Primary cutaneous amyloidosis (PCA) is a relatively common skin disorder among Asians and South Americans. It is usually diagnosed clinically. However, for cases with atypical presentations, the diagnosis can be a challenge and skin biopsy may be necessary. Dermoscopy has been proved to be a valuable, noninvasive tool in the diagnosis of cutaneous pigmented diseases. Most lesions of PCA show hyperpigmentation and the major histopathological abnormalities of PCA occur in the epidermis and dermal papillae. Dermoscopy might be a powerful tool to provide valuable information for the diagnosis of PCA.
Objectives We aimed to find characteristic dermoscopic features of PCA.
Materials and methods Cases with typical clinical presentations of PCA, either macular or lichen subtypes, were included in this study. All were evaluated using a hand-held, polarized and nonpolarized dermoscope.
Results A total of 35 patients with clinically diagnosed PCA were enrolled. Eighteen patients had lesions consistent with macular amyloidosis and 17 with lichen amyloidosus. We found two major dermoscopic patterns characteristic of PCA. The most common dermoscopic finding of PCA was a central hub, which could be either white or brown, surrounded by various configurations of pigmentation. For cases of lichen amyloidosus with prominent hyperkeratosis, the central hub was replaced by a scar-like morphology.
Conclusions This is the first study to report the characteristic dermoscopic features of PCA. We demonstrate that the use of a dermoscope may assist in achieving an accurate diagnosis of PCA.

Introdcution

Primary cutaneous amyloidosis (PCA) is a relatively common skin disorder among Asians and South Americans.^[1,2] As it is a pruritic and potentially disfiguring disorder, this disease may impact greatly on a patient's social and emotional status. There are several subtypes of PCA and its classification is based on different clinical appearances. The most common subtypes are macular amyloidosis (MA) and lichen amyloidosus (LA), or a mixed subtype of the two (biphasic amyloidosis).^[3] Other rare forms include anosacral amyloidosis^[4] and amyloidosis cutis dyschromica.^[5] LA presents discrete, firm, hyperkeratotic, closely set, pinhead- to matchhead-sized, dome-shaped, brownish papules, while MA shows smaller brownish macules in a rippling pattern.

In Taiwan PCA is usually diagnosed clinically due to its common occurrence (mean 1-year prevalence, 0·98 per 10 000 persons).^[6,7] However, similar clinical pictures do occur in other cutaneous diseases. Differential diagnosis of PCA should include lichen simplex chronicus, post-inflammatory hyperpigmentation, prurigo nodularis and colloid milium. 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.

Dermoscopy has proved to be a valuable, noninvasive tool in the diagnosis of cutaneous pigmented diseases, as well as skin malignancies.^[8–10] It magnifies the colour and structure in the epidermis, dermoepidermal junction and papillary dermis. Although PCA is not classified as a type of 'pigmented disorder', most lesions of MA or LA show hyperpigmentation. In addition, the major histopathological abnormalities of PCA occur in the epidermis and dermal papillae. Therefore, we believe that dermoscopy could be a powerful tool to provide valuable information for the diagnosis of PCA. However, dermoscopic findings of PCA have never been reported before; to our knowledge, this is the first report in the literature. In this study, we present characteristic dermoscopic features of 35 patients with PCA and demonstrate the value of dermoscopy in the diagnosis of PCA.