Primary Systemic Amyloidosis Characterized by Multiple Keratinous Cysts: A Case Report.

A 67-year-old male presented with plaques around the orbit and ecchymosis on the neck and back of hands for 2 years. Physical examination showed seborrheic-keratosis-like plaques around the orbit, ecchymosis on the neck and back of hands, as well as nail dystrophy. Serum λ light chain was positive. Histopathological examination demonstrated multiple keratinous cysts in the dermis and eosinophilic homogeneous material in the dermis, which was positive for Congo red with apple-green birefringence on polarized light. Kidney biopsy showed deposition of acellular eosinophilic material in the arteriole wall. Congo red staining was positive. A bone marrow biopsy revealed multiple myeloma. The diagnosis of primary systemic amyloidosis with multiple myeloma was made.