Amyloidosis Cutis Dyschromica: A Rare Subtype of Primary Cutaneous Amyloidosis with Dermoscopy

Sir,

Amyloidosis cutis dyschromica (ACD) is a rare, chronic, progressive variant of primary cutaneous amyloidosis (PCA). It was first described by Morishima in 1970.[1] It is characterized by both diffuse hyperpigmentation and hypopigmentation, prepubertal onset and focal amyloid deposits in the papillary dermis. Herein, we report a case series of three patients with ACD in which the patients presented with dyschromia skin where dermoscopy and histopathology with special staining helped in diagnosing. The patient characteristics are given in the table [Table 1] [Figure 1a-d].

Table 1.

Patient characteristics

Age/Sex	Presentation	Duration	Distribution	Symptoms	Dermoscopy	Histopathology
34/F	Diffuse hyperpigmentation with mottled spotty, well-defined, de-pigmented macules ranging from pinpoint to 1 cm in size.	Since childhood (More since last 5 years)	Started from abdomen and	Mildly pruritic and no associated, erythema, telangiectasia, atrophy, or blisters.	Ill-defined hypopigmented patches and hyperpigmented blotches and patches	Hyperkeratosis, widened papillary dermis with deposits of eosinophilic material positive for methyl violet
28/F	Hyperpigmentation and hypopigmented macules	7 years	On the trunk initially, gradually involved both upper arms.	Asymptomatic	ill-defined hypopigmented patches and surrounding brown blotches.	Hyperkeratosis, pigment incontinence and eosinophilic deposits in papillary dermis.
24/F	Diffuse hyperpigmentation and spotty hypopigmented macules in between	Since 1 year of age	Hyperpigmentation on the back followed by mottles hypo- and hyperpigmented macules on the trunk, face and upper limbs	Asymptomatic	Well-demarcated hypopigmented patches and macules and peripheral brown blotches.	Hyperkeratosis, melanophages and small amorphous deposits in papillary dermis positive for methyl violet.

Figure 1.

Clinical Image. (a and b) Patient 1 showing multiple depigmented macules distributed over a background hyperpigmentation over the trunk. (c) Patient 2 showing hyperpigmentation with depigmented macules over trunk and (d) Patient 3 with facial and trunk involvement

ACD is a variant of PCA, characterized primarily by reticular asymptomatic hyperpigmented and hypopigmented macules over the body, pre-pubertal onset and amyloid deposits in the dermis.[1] Other rare variants of PCA include familial poikiloderma-like cutaneous amyloidosis, bullous, vitiliginous and anosacral variant.[2] The exact pathogenesis is unknown. It is proposed that hypersensitivity to Ultraviolet B (UVB) damage in addition to DNA repair defects plays a key role in the causation of dyschromia. However, it is still a debatable aetiology.[3] The damaged keratinocytes are phagocytosed by the histiocytes and the fibroblasts generating amyloid deposition.[4]

Additionally, prepubertal onset and the familial cases suggest genetic aetiology.[4]

Recently, loss-of-function mutation in Glycoprotein non-metastatic melanoma protein B (GPNMB), encoding glycoprotein non-metastatic melanoma protein B (which is important for melanosome formation, autophagy, phagocytosis and tissue repair) was found in autosomal-recessive cases of ACD, providing insights into the pathogenesis of amyloidosis and dyschromia.[5]

Clinical differentials of ACD include dyschromatosis universalis hereditaria, xeroderma pigmentosum and poikiloderma-like amyloidosis. However, the first two entities do not show amyloid deposition and poikilodermatous amyloidosis has additional features of poikiloderma, brownish lichenoid papules, vesicles, photosensitivity, palmoplantar keratosis and short stature in its syndromic variant apart from amyloid deposits.[6,7]

Dermoscopy of our patients showed ill-defined hypopigmented patches, white grid-like stripes and hyperpigmented blotches and patches. Wang et al.,[8] in their report, discussed similar features [Figure 2a, 2b]. Various differentials of ACD and their reported dermoscopic findings have been mentioned in Table 2.

Figure 2.

(a and b) Dermoscopy using DermLite DL4 showing ill-demarcated hypopigmented patches and macules interspersed between brown blotches and spots giving the surrounding hyperpigmentation. [10x, polarized] (c) Histopathology showing hyperkeratosis, pigment incontinence, melanophages and widened papillary dermis. [H and E, 40x), and (d) deposition of eosinophilic material in the papillary dermis. [methyl violet, 40x)

Table 2.

Dermoscopic features of the differentials of ACD

Clinical Differential	Dermoscopic findings
Amyloidosis cutis dyschromica[6]	Patchy white hypopigmentation and brownish spots, stripes, or hyperpigmented blotches and patches
Dyschromatosis symmetrica hereditaria[9]	Multiple hyperpigmented brownish spots with different dimensions are characterized by a coarse grid of brown lines over a diffuse light brown background.
Xeroderma pigmentosa[10]	Asymmetrical blotch, atypical network, hyperpigmented follicular openings, pigmented rhomboidal areas.
Dyskeratosis congenita[11]	Pigmented lines, brown dots and globules in netlike pattern.
Lichen planus pigmentosus[12]	Brown pseudonetwork, hem-like pattern, speckled dots and globules in various patterns, perifollicular deposition.

Histopathology in our cases revealed hyperkeratosis, pigment incontinence, melanophages and widened papillary dermis with deposition of eosinophilic material in the papillary dermis which stained positive with methyl violet [Figure 2c, 2d]. Our findings were consistent with the histopathology findings by other authors.[1]

Various therapeutic modalities have been used in ACD including topical corticosteroids, capsaicin, keratolytics, UVB, Psoralen and UVA (PUVA) therapy, dermabrasion and CO2 laser, in addition to strict photoprotection and use of broad-spectrum sunscreen with variable results. Acitretin has been used effectively in ACD. It causes apoptosis of damaged keratinocytes, thus preventing amyloid formation. Additionally, it also causes phagocytosis of already deposited amyloid.[1] We started our patients on combination therapy with oral Acitretin and topical corticosteroids, and as expected, all the patients showed moderate improvement at 3 months follow-up.

Informed consent

Written informed consent from the patients for the use of images and publication of their details were obtained.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.