Secondary cutaneous amyloidosis in disseminated superficial porokeratosis: a case report

Disseminated superficial porokeratosis (DSP) is a rare cause of secondary cutaneous amyloidosis. An 83-year-old male patient showed an increase in both size and number of DSP lesions after contracting pulmonary tuberculosis. The DSP lesions of the patient consisted of numerous annular eruptions on both sun-exposed and sun-protected areas, which occurred over a period of 20 years. Multiple skin biopsies were taken from normal or lesional/sun-exposed or sun-protected skin samples. Histopathologic examination included routine H&E stains, Congo red stains, thioflavin-T stains and anticytokeratin antibodies (AE1, AE3). And the results were as follows; 1) Positive staining with Congo red and thioflavin-T indicated an amyloid nature for the deposits, 2) confinement of the amyloid deposition just below the lesional epidermis (while sparing the neighboring uninvolved or distant normal skin) indicated some role of the lesional epidermis, and 3) positive staining with AE3 further indicated an epidermal origin-type II epithelial keratin-of the amyloid. We present a case of DSP with a local amyloid deposit, characterized by association of positive familial background, severe pruritus and pulmonary tuberculosis.