Immunohistochemical Demonstration of Hyalinosis-Associated 90 kD Glycoprotein in Amyloid Deposits of Lichen Amyloidosus

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Immunohistochemical methods were used to study the nature of the amyloid deposits in lichen amyloidosus, in nodular amyloidosis, and in the cutaneous amyloid deposits found in Finnish-type systemic amyloidosis. In every case the anti-keratin serum stained the epidermis and sweat ducts but not the amyloid itself. None of the amyloids stained with anti-sera to prealbumin, to serum amyloid A protein, or to the free kappa or lambda light chains of immunoglobulins. In lichen amyloidosus but not in the other types of amyloidosis the amyloid substance stained intensely with the anti-serum to 90 kD glycoprotein. This glyco-protein, which is present in the basal cells of the hair follicles of normal skin, was first isolated from the extensive cutaneous deposits of a patient with a nonamyloid disease. The demonstration of this glycoprotein in lichen amyloidosus but not in nodular amyloidosis suggest a difference in pathogenesis between the two diseases. Tests for 90 kD glycoprotein may prove to be of value in the differential diagnosis of cutaneous amyloidosis.