Histologic features of specimens of skin from 40 patients with systemic amyloidosis were correlated with the clinical findings. In primary systemic amyloidosis (including patients with myeloma) papules were correlated with amyloid deposits in dermal papillae, plaques with diffuse involvement of the corium, and nodules and tumefactions with infiltration of the reticular corium and subcutaneum. In patients with purpura, amyloid was deposited in the walls of dermal blood vessels. There was involvement of pilosebaceous units in all biopsy specimens from areas of alopecia. The electron microscopic appearance of the amyloid in skin in primary systemic amyloidosis was similar to that found in localized forms of cutaneous amyloidosis.
Among 100 patients with secondary systemic amyloidosis who came to autopsy, no instance could be found of a clinical lesion caused by the deposition of amyloid in the skin. Among 60 clinical examples of cutaneous amyloidosis, no patient was found to have secondary systemic amyloidosis. Thus, when a dermatologic lesion is attributable to amyloid, an aggressive search for such conditions as tuberculosis is unwarranted, since secondary systemic amyloidosis would be a most unlikely cause. When a dermatosis is present in a patient with secondary systemic amyloidosis it may be related to the underlying disorder, but it is almost certainly not caused by amyloid.
Brownstein MH, Helwig EB. The Cutaneous AmyloidosesII. Systemic Forms. Arch Dermatol. 1970;102(1):20-28. doi:10.1001/archderm.1970.04000070022003