Two asymptomatic lesions that had been present for 1 year on the left upper chest of a 61-year-old man were excised. Pathologic examination revealed the raised, dark brown medial lesion to be an interdermal nevus; the lateral, light tan lesion with papules (arrow) was a papillomatous interdermal nevus with primary macular amyloidosis.
Dr Robert P. Blereau of Morgan City, La, writes that amyloidosis may be systemic or cutaneous. The skin may be involved in systemic disease; however, skin manifestations more commonly represent cutaneous amyloidosis. Systemic amyloidosis can occur as primary and myeloma-associated diseases, as a secondary disorder associated with other chronic diseases, in several heredofamilial forms, and as amyloid elastosis. Localized cutaneous amyloidosis may manifest as lichen, macular, and biphasic variants; nodules; poikilodermatosis; and familial cutaneous or secondary localized forms.
The cause of amyloid production is not known; a variety of mechanisms may be responsible for the characteristic amyloid deposition patterns of the numerous forms of the disease.
When examined under light microscopy, Congo red'stained amyloid fluoresces a characteristic apple green color; amyloid stains pink with hematoxylin and eosin. Immunoglobulins, particularly IgM and C3 complement, are found in cutaneous amyloid.1
Lichen and macular amyloidosis, which can transform from one to the other, are variants of the same process and have no visceral involvement. Microscopic examination of amyloid from patients with either of these forms of disease shows straight, nonbranching filaments in random array with basal epidermal cell involvement. Lichen amyloidosis has a predilection for extensor surfaces of the lower extremities; macular disease is less common and occurs mainly on the trunk.
1. Weedon D. Skin Pathology. Edinburgh: Churchill Livingstone; 1997:359-362.