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Dermatology Made Easy is based on the most popular topics from DermNet NZ's vast array of material. The book combines the essential focus of the ‘Made Easy’ book series with the authority and knowledge base of DermNet NZ's unparalleled resources.
Author: Caroline Mahon, Locum Consultant Dermatologist in Adult and Paediatric Dermatology, Bristol Royal Infirmary, Bristol, United Kingdom. DermNet New Zealand Editor in Chief: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Maria McGivern. July 2017.
Amyloidosis is a group of disorders in which amyloid protein is deposited in various tissues. It includes:
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 .
*See figure legends at end of article
ACD is rare. At the time of writing, about 50 cases have been reported in the medical literature .
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.
ACD causes slowly progressive localised hyperpigmentation and hypopigmentation (dyschromia or dyschromatosis).
The specific findings that distinguish ACD from the more common macular and lichenoid variants of primary cutaneous amyloidosis are:
What are the complications of amyloidosis cutis dyschromica?
There are no known complications from ACD.
ACD is diagnosed by recognising the typical clinical features, and confirmed by the biopsy of a hyperpigmented or hypopigmented macule.
*See figure legends at end of article
ACD may closely resemble a number of other rare dyschromatoses; these include:
Other conditions that should be excluded include:
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 .
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.
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