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Skin-nontumor

Other dermatoses

Amyloidosis


Reviewer: Mowafak Hamodat MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns (Canada) (see Reviewers page)
Revised: 18 July 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Clinical features
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● In primary localized cutaneous amyloidosis, by definition, there is no systemic or other dermatologic disorder
● Either macular (Central/South America, India, Middle East), lichenoid (China), biphasic or nodular
Macular: moderately pruritic dark brown papules in reticulated or rippled pattern, symmetric over upper back and arms
Lichenoid: intensely pruritic, discrete, firm, hyperkeratotic plaques and papules of anterior shins and extensor forearms, with amyloid deposits in papillary dermis accompanied by hyperkeratosis, papillomatosis and epidermal hyperplasia
Biphasic: lichenoid and macular
● To differentiate between amyloid AA and other types, use potassium permanganate reaction; amyloid AA does not stain with Congo Red after potassium permanganate, but others do (Am J Pathol 1979;97:43)

Case reports
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● 27 year old man with hyperpigmented black patches on upper back and limbs (Arch Pathol Lab Med 2005;129:697)
● 72 year old woman with 20 year history of easy eyelid bruising (Dermatology Online Journal; 1995:1(2))

Clinical images
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Facial involvement


Figure 1: flat, dusky brown patch of upper back; 2: Sirius red+ amorphous material; 3: cytoplasm is cytokeratin MNF+

Micro description
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● Primary amyloidoisis: masses of eosinophilic, amorphous, fissured material in dermis and subcutaneous tissue
● Macular amyloidosis: focal / small amounts of eosinophilic faceted deposits in papillary dermis; also pigment incontinence
● Lichenoid amyloidosis: hyperkeratosis, acanthosis, basal hydropic degeneration; small eosinophilic globules in papillary dermis; also mild chronic inflammatory cell infiltrate, pigment incontinence

Micro images
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Various images

   
Congo Red staining without (left) and with (right) polarization microscopy

   
Congo Red staining (left) and Thioflavin-T staining with fluorescent microscopy (right)

Positive stains
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● Congo Red shows apple–green birefringence under polarized light
● Methyl or cresyl violet
● Thioflavin–T with examination using fluorescence microscopy

Electron microscopy
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● Straight non branching amyloid filaments with a diameter of 6–10 nm showing a hollow core on cross section
● Infra red microscopy reveals a beta–pleated antiparallel configuration

Electron microscopy images
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Mesh-like pattern consisting of 6-10 nanometer non-branching fibrils diagnostic of amyloid

Additional references
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eMedicine

End of Skin-nontumor > Other dermatoses > Amyloidosis


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