Peculiar progressive plaques

Abstract

Conflict of interest: none declared. A 66‐year‐old man presented for assessment of a pigmented lesion that had been gradually changing in appearance. Clinically, the lesion was a malignant melanoma, which was excised. As an incidental finding, 10 smooth, orange‐red plaques were noted on the back and trunk (Fig. 1). They had been present for at least 10 years, slowly increasing in size, and milia could be seen within the plaques (Fig. 2). They were otherwise asymptomatic. The patient had numerous seborrhoeic keratoses. The clinical suspicion of plaque‐type amyloid was confirmed histologically. Haematoxylin and eosin staining showed amorphous globules of eosinophilic material in the upper dermis, suggestive of amyloid. The dermal material stained positive for a variety of amyloid stains (Congo red, crystal violet and thioflavin T). Results of laboratory investigations, including full blood count, serum creatinine, electrophoresis, immunoglobulins and urinalysis were normal. Amyloidosis occurs in many tissues due to extracellular accumulation of the proteinaceous substance composed of often biochemically unrelated proteins bound to a fibrillar substance (amyloid P component).1 There are two common types, amyloid of unknown origin (AA amyloid) often a result of chronic sepsis or inflammation, and amyloid of light‐chain origin (AL amyloid).