Amyloidosis cutis dyschromica
What is amyloidosis?
Amyloidosis is a group of disorders in which amyloid protein is deposited in various tissues. It includes:
- Systemic amyloidosis, which involves a variety of organs
- Primary cutaneous amyloidosis in which only the skin is affected.
What is amyloidosis cutis dyschromica?
Amyloidosis cutis dyschromica (ACD) is a form of primary cutaneous amyloidosis that causes localised hyperpigmentation and hypopigmentation.
ACD was first described by a Japanese dermatologist, Morishima in 1970 .
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Who gets amyloidosis cutis dyschromica?
ACD is rare. At the time of writing, about 50 cases have been reported in the medical literature .
- Males and females are equally affected.
- Most patients first develop the skin pigment changes in early childhood.
- The majority of patients (77%) have a family history of similar pigment alteration.
- Most cases (63%) have occurred in people of East Asian (Chinese, Hong Kong Chinese and Taiwanese) or South-East Asian (Thai, Filipino and Indonesian) ethnicity.
- ACD is also commonly seen in people of Indian and Pakistani heritage.
- Only three cases of ACD have been reported in Caucasian patients.
What causes amyloidosis cutis dyschromica?
ACD is caused by the deposition of amyloid derived from degenerate or damaged keratinocytes (epidermal skin cells). The reason that the keratinocytes degenerate and how this relates to loss and gain of pigment in the affected areas of skin are not clear. A genetic cause is likely.
What are the clinical features of amyloidosis cutis dyschromica?
ACD causes slowly progressive localised hyperpigmentation and hypopigmentation (dyschromia or dyschromatosis).
- In most cases, the onset of the pigment change is in childhood, although in some the changes are not noted until adulthood.
- The dyschromia does not affect palms, soles and mucosal surfaces.
- Facial involvement is uncommon (approximately 10%) .
The specific findings that distinguish ACD from the more common macular and lichenoid variants of primary cutaneous amyloidosis are:
- Dotted, reticular or diffuse hyperpigmentation mixed with ‘lentil-sized’ hypopigmented macules.
- Mild or no associated pruritus.
What are the complications of amyloidosis cutis dyschromica?
There are no known complications from ACD.
How is amyloidosis cutis dyschromica diagnosed?
ACD is diagnosed by recognising the typical clinical features, and confirmed by the biopsy of a hyperpigmented or hypopigmented macule.
- Amyloid deposits are present within the papillary dermis just below the epidermis.
- They may be very subtle and difficult to see with haematoxylin and eosin (H&E) staining so Congo red staining is required.
- Using polarised light, apple-green-coloured birefringence of the amyloid material may be seen on microscopic examination.
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What is the differential diagnosis for amyloidosis cutis dyschromica?
ACD may closely resemble a number of other rare dyschromatoses; these include:
- Dyschromatosis universalis hereditaria
- Dyschromatosis symmetrica hereditaria
- Cutis tricolor
- Epidermolysis bullosa simplex with mottled pigmentation
- Tertiary pinta.
Other conditions that should be excluded include:
- Dyskeratosis congenita, which presents with nail dystrophy, oral leukoplakia and bone marrow failure in childhood
- Xeroderma pigmentosum, which causes marked cutaneous and ocular photosensitivity and childhood-onset aggressive skin cancers
- Degos disease, a potentially life-threatening vasculopathy.
What is the treatment for amyloidosis cutis dyschromica?
No therapeutic intervention has been demonstrated to be of benefit in ACD. Multiple topical treatments, including 10% urea cream and tazarotene , have been prescribed to patients without significant improvement. Oral vitamin C and vitamin E supplements have had minimal benefit . Acitretin has been prescribed in a small number of cases, with a modest improvement reported in approximately 85% of cases .
What is the outcome for amyloidosis cutis dyschromica?
ACD is typically gradually progressive. The dyschromia may eventually involve almost all of the skin except the palms, soles of the feet, and oral and genital mucosa. Alternatively, ACD can progress gradually in localised areas, and it is often more prominent in areas of skin overlying bony prominences and joint surfaces.
Figure 1. Multiple dotted areas of hypopigmentation on a background of patchy hyperpigmentation overlying the elbow of a patient affected by amyloidosis cutis dyschromica.
Figure 2. Multiple subtle dotted areas of hypopigmentation on a background of patchy hyperpigmentation on the lower leg of a patient affected by amyloidosis cutis dyschromica.
Figure 3. A close-up image of the pigmentary change on the lower leg of a patient affected by amyloidosis cutis dyschromica.
Figure 4. A skin biopsy showing very subtle pink globules just underneath the epidermis in amyloidosis cutis dyschromica.
Figure 5. A skin biopsy stained with Congo red staining, which highlights the amyloid deposits seen with amyloidosis cutis dyschromica.
Figure 6. A skin biopsy Congo red-stained specimen viewed under polarised light microscopy showing apple-green birefringence of the amyloid material that is characteristic of amyloidosis cutis dyschromica.