Characteristic Dermoscopic Features of Primary Cutaneous Amyloidosis

A Study of 35 Cases

Y.Y. Chuang; D.D. Lee; C.S. Lin; Y.J. Chang; M. Tanaka; Y.T. Chang; H.N. Liu

Disclosures

The British Journal of Dermatology. 2012;167(3):548-554. 

In This Article

Results

A total of 35 clinically diagnosed PCA patients were enrolled. Eighteen patients had lesions consistent with MA, and 17 with LA. Ten patients, including four cases of MA and six of LA, underwent skin biopsy and their histopathological findings were compatible with PCA, including basal hyperpigmentation, pigment incontinence, and amyloid deposition in the papillary dermis. In addition, compact orthohyperkeratosis and acanthosis were also found for most LA specimens.

Macular Amyloidosis

The dermoscopic findings of all 18 cases of MA shared a common feature, i.e. each 'macule' was composed of a central hub surrounded by brownish pigmentation. The colour of the central hub could be white or brown, and both colours could be found in the same patient. Eleven patients showed white central hubs, four patients brown, and three had both (Table 1). Figure 1 demonstrates three different configurations of brownish pigmentation around the central hubs, including fine streaks (Fig. 1b), leaf-like extensions (Fig. 1e) and a noncircular thick pedal projection with a smooth border (Fig. 1g).

Figure 1.

Three cases of macular amyloidosis. Patient 1: (a) multiple rippling brownish macules on the lower right leg. (b) The dermoscopic findings revealed multiple uniform small central hubs with brown fine streaks radiating from the centre. The colour of the central hubs was brown in this case. (c) The pathology demonstrated basket-weave orthokeratosis, basal hyperpigmentation, pigment incontinence, and amyloid deposition in the upper dermis. The amyloid was pink in colour with Congo red staining (× 100). Patient 2: (d) clinical picture. (e) The dermoscopic pattern showed a venation-like extension of pigmentation from each white central hub. Patient 3: (f) clinical picture. (g) For each macule, the dermoscopic picture demonstrated a noncircular thick pedal projection with a smooth border extending from a white central hub.

Lichen Amyloidosus

In 17 cases of LA, seven patients showed the above-mentioned 'central hub' pattern seen in MA and all possessed whitish central hubs. In the other 10 cases, the central hub was replaced by a whitish scar-like centre and we designated this pattern as 'scar-like' (Table 1). In three, the centre was surrounded by some brownish dots or a rim of white collarette, resembling a volcanic crater (Fig. 2). Where the papules were even larger and thicker, each papule sometimes became a completely structureless area (n = 7) (Fig. 3). Of the seven cases with central hubs, three also revealed the 'scar-like' dermoscopic pictures for some lesions.

Figure 2.

The clinical picture of a patient with lichen amyloidosus (a). Under dermoscopy, each papule showed a whitish scar-like centre surrounded by some brownish dots (arrows) or a rim of white collaret (arrowhead). The entire picture resembled a volcanic crater (b). The pathology showed compact orthohyperkeratosis, acanthosis and amorphous amyloid deposits with melanin granules in the dermal papillae (c). Haematoxylin and eosin; × 400.

Figure 3.

A case of lichen amyloidosus. (a) Clinical picture. (b) In this patient with larger papules, the central hub was completely replaced by a scar-like structureless area. (c) The structureless area correlated with the extremely thick orthohyperkeratosis. Haematoxylin and eosin; × 100.

Correlations Between Dermoscopic and Histopathological Findings

Ten cases underwent skin biopsy and we tried to associate the dermoscopic features with their histopathological findings. We found, in either MA or LA, that the brown pigmentation under dermoscopy was due to basal hyperpigmentation, pigment incontinence and melanin granules within amyloid deposition in the dermal papilla (Figs 1b,c and 2b,c). These pathological changes have been observed persistently in the pathology of PCA.[13] Besides, there was loose, basket-weave orthokeratosis in the lesions showing brown central hubs (Fig. 1b,c). The central hub looked white rather than brown if there was marked hyperkeratosis. In most cases of LA, the central hubs disappeared and were replaced by whitish scar-like centres, corresponding to the pathological change of compact orthohyperkeratosis and acanthosis (Fig. 2b,c). In these, as the horny layer was even thicker, a completely structureless area predominated (Fig. 3b,c).

Friction Melanosis and Lichen Simplex Chronicus

We also examined a case of friction melanosis and a case of lichen simplex chronicus, which often mimic PCA clinically. The dermoscopic findings of friction melanosis revealed a fine brownish stippling in a reticular network without the distinctive central hubs (Fig. 4). Under the dermoscope, lichen simplex chronicus demonstrated accentuated skin markings with mottled light brownish and white pigmentary change over the entire field of examination (Fig. 5). No characteristic central hubs or scar-like composition such as those in MA or LA was observed.

Figure 4.

A case of friction melanosis. (a) This clinical picture is of the back, and the lesion greatly mimicked macular amyloidosis. (b) Dermoscopy showed fine brownish stippling on a ripple reticular network, but without central hubs.

Figure 5.

A case of lichen simplex chronicus. (a) An erythematous to brownish plaque with lichenification. (b) Dermoscopy demonstrated accentuated skin markings with mottled light brownish and white pigmentary change over the entire field of examination.

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