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Case Reports

Abstract

Primary or light chain (AL) amyloidosis is a systemic depositional disorder seen in association with multiple myeloma or other plasma cell dyscrasias that commonly involves the skin in addition to internal organs. Cutaneous biopsy, generally from the abdominal fat pad or minor salivary gland, serves as a minimally invasive method to confirm the diagnosis in suspected cases. Histopathology characteristically shows amyloid deposits in the dermis and subcutis, most often in a perivascular distribution, but deposits can involve adnexal structures. We present a unique case of AL systemic amyloidosis with amyloid deposition localized exclusively to adnexal structures, otherwise sparing the vasculature, dermis and subcutis. A 66-year-old male with lambda dominant paraproteinemia and renal biopsy suspicious for AL amyloidosis underwent diagnostic abdominal fat pad biopsy. No skin, mucosal, hair or nail findings were noted on examination. Histologic sections demonstrated amorphous pink material surrounding numerous hair follicles and eccrine coils throughout the specimen highlighted by Congo Red staining with apple green birefringence on polarized microscopy. The specimen was negative for amyloid deposition in the dermis, subcutis and vascular structures. Mass spectrometry confirmed a diagnosis of AL lambda amyloidosis. Treatment was initiated with combination daratumumab, bortezomib, cyclophosphamide and dexamethasone (D-VCd). Repeat fat pad biopsy obtained four months into treatment to assess response was negative for amyloid. This case highlights a unique and subtle histopathological presentation of AL amyloidosis. Dermatopathologists should be aware that systemic amyloidosis can present with deposition of amyloid material in an exclusively perifollicular and perieccrine pattern, which can be histologically subtle.