There is adeep dermal and subcutaneous amorphous eosinophilic infiltrate. The primary and myeloma associated amyloidosis are due to deposition of AL protein, which are made up of immunoglobulin light chains. In secondary, or reactive amyloidosis, the amyloid protein is designated as AA, and is felt to be an acute-phase reactant. Numerous disease states, including chronic infections, autoimmune diseases, malignancy and even chronic dermatosis may be associated with reactive amyloidosis.
Cutaneous involvement is rare in secondary amyloidosis.
Amyloidosis can also be localized to various organ systems, including the skin. It is considered a cutaneous plasmacytoma, and the deposits are made of AL protein. Macular amyloidosis presents with brown patches made up of macules that coalesce in a rippled appearance, usually on the upper back, but also on the extren-fities, chest and buttocks. Pruritus is frequently present. Lichen amyloidosis is a pruritic eruption consisting of hyperkeratotic papules, usually on the shins.