Macular amyloidosis is seen most frequently on the upper back, and is characterized
by irregular pigmentation and pruritus. It is thought that lichen amyloidosis,
which occurs most frequently in the legs as papules or plaques, may represent
macular amyloidosis with superimposed epidermal hyperplasia secondary to
rubbing, picking, or scratching (secondary lichenification). Small deposits
of amyloid are found in the papillary dermis in either condition, and such
deposits may be overlooked on cursory examination of a slide. Pigment incontinence
is usually seen. One occasionally finds a few apoptotic keratinocytes.
It is thought that the amyloid may be partly derived from the products
of apoptotic necrosis. As a side note, it is interesting that amyloid formation
is not seen as part of the classical lichenoid reaction
of skin, though the apoptotic keratinocytes (Civatte bodies) may persist
as such when the inflammatory reaction has subsided.
High power showing amyloid (small arrows) and an
apoptotic keratinocyte (large arrow). Pigment incontinence also present.
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